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tests/results/22
606 строк
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Igor Chubin
updated tests
06 авг 2020, 08:28
06 авг 2020, 08:28
1c3bec6
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[38;5;246;03m// Single-line comments start with two slashes.[39;00m [38;5;246;03m/* Multiline comments start with slash-star,[39;00m [38;5;246;03m and end with star-slash */[39;00m [38;5;246;03m// Statements can be terminated by ;[39;00m [38;5;252mdoStuff[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;246;03m// ... but they don't have to be, as semicolons are automatically inserted[39;00m [38;5;246;03m// wherever there's a newline, except in certain cases.[39;00m [38;5;252mdoStuff[39m[38;5;252m([39m[38;5;252m)[39m [38;5;246;03m// Because those cases can cause unexpected results, we'll keep on using[39;00m [38;5;246;03m// semicolons in this guide.[39;00m [38;5;246;03m///////////////////////////////////[39;00m [38;5;246;03m// 1. Numbers, Strings and Operators[39;00m [38;5;246;03m// JavaScript has one number type (which is a 64-bit IEEE 754 double).[39;00m [38;5;246;03m// Doubles have a 52-bit mantissa, which is enough to store integers[39;00m [38;5;246;03m// up to about 9✕10¹⁵ precisely.[39;00m [38;5;67m3[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 3[39;00m [38;5;67m1.5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 1.5[39;00m [38;5;246;03m// Some basic arithmetic works as you'd expect.[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 2[39;00m [38;5;67m0.1[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;67m0.2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 0.30000000000000004[39;00m [38;5;67m8[39m[38;5;252m [39m[38;5;252m-[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 7[39;00m [38;5;67m10[39m[38;5;252m [39m[38;5;252m*[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 20[39;00m [38;5;67m35[39m[38;5;252m [39m[38;5;252m/[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 7[39;00m [38;5;246;03m// Including uneven division.[39;00m [38;5;67m5[39m[38;5;252m [39m[38;5;252m/[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 2.5[39;00m [38;5;246;03m// And modulo division.[39;00m [38;5;67m10[39m[38;5;252m [39m[38;5;252m%[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 0[39;00m [38;5;67m30[39m[38;5;252m [39m[38;5;252m%[39m[38;5;252m [39m[38;5;67m4[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 2[39;00m [38;5;67m18.5[39m[38;5;252m [39m[38;5;252m%[39m[38;5;252m [39m[38;5;67m7[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 4.5[39;00m [38;5;246;03m// Bitwise operations also work; when you perform a bitwise operation your float[39;00m [38;5;246;03m// is converted to a signed int *up to* 32 bits.[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m<<[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 4[39;00m [38;5;246;03m// Precedence is enforced with parentheses.[39;00m [38;5;252m([39m[38;5;67m1[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;67m3[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m*[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 8[39;00m [38;5;246;03m// There are three special not-a-real-number values:[39;00m [38;5;70;01mInfinity[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// result of e.g. 1/0[39;00m [38;5;252m-[39m[38;5;70;01mInfinity[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// result of e.g. -1/0[39;00m [38;5;70;01mNaN[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// result of e.g. 0/0, stands for 'Not a Number'[39;00m [38;5;246;03m// There's also a boolean type.[39;00m [38;5;70;01mtrue[39;00m[38;5;252m;[39m [38;5;70;01mfalse[39;00m[38;5;252m;[39m [38;5;246;03m// Strings are created with ' or ".[39;00m [38;5;214m'abc'[39m[38;5;252m;[39m [38;5;214m"Hello, world"[39m[38;5;252m;[39m [38;5;246;03m// Negation uses the ! symbol[39;00m [38;5;252m![39m[38;5;70;01mtrue[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;252m![39m[38;5;70;01mfalse[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// Equality is ===[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;67m2[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;246;03m// Inequality is !==[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m!==[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;67m2[39m[38;5;252m [39m[38;5;252m!==[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// More comparisons[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m<[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;67m1[39m[38;5;252m [39m[38;5;252m>[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;67m2[39m[38;5;252m [39m[38;5;252m<=[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;67m2[39m[38;5;252m [39m[38;5;252m>=[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// Strings are concatenated with +[39;00m [38;5;214m"Hello "[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;214m"world!"[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello world!"[39;00m [38;5;246;03m// ... which works with more than just strings[39;00m [38;5;214m"1, 2, "[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;67m3[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "1, 2, 3"[39;00m [38;5;214m"Hello "[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252m[[39m[38;5;214m"world"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m"!"[39m[38;5;252m][39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello world,!"[39;00m [38;5;246;03m// and are compared with < and >[39;00m [38;5;214m"a"[39m[38;5;252m [39m[38;5;252m<[39m[38;5;252m [39m[38;5;214m"b"[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// Type coercion is performed for comparisons with double equals...[39;00m [38;5;214m"5"[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;70;01mnull[39;00m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;70;01mundefined[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// ...unless you use ===[39;00m [38;5;214m"5"[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;70;01mnull[39;00m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;70;01mundefined[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;246;03m// ...which can result in some weird behaviour...[39;00m [38;5;67m13[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252m![39m[38;5;67m0[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// 14[39;00m [38;5;214m"13"[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252m![39m[38;5;67m0[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// '13true'[39;00m [38;5;246;03m// You can access characters in a string with `charAt`[39;00m [38;5;214m"This is a string"[39m[38;5;252m.[39m[38;5;252mcharAt[39m[38;5;252m([39m[38;5;67m0[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 'T'[39;00m [38;5;246;03m// ...or use `substring` to get larger pieces.[39;00m [38;5;214m"Hello world"[39m[38;5;252m.[39m[38;5;252msubstring[39m[38;5;252m([39m[38;5;67m0[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello"[39;00m [38;5;246;03m// `length` is a property, so don't use ().[39;00m [38;5;214m"Hello"[39m[38;5;252m.[39m[38;5;252mlength[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 5[39;00m [38;5;246;03m// There's also `null` and `undefined`.[39;00m [38;5;70;01mnull[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// used to indicate a deliberate non-value[39;00m [38;5;70;01mundefined[39;00m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// used to indicate a value is not currently present (although[39;00m [38;5;252m [39m[38;5;246;03m// `undefined` is actually a value itself)[39;00m [38;5;246;03m// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.[39;00m [38;5;246;03m// Note that 0 is falsy and "0" is truthy, even though 0 == "0".[39;00m [38;5;246;03m///////////////////////////////////[39;00m [38;5;246;03m// 2. Variables, Arrays and Objects[39;00m [38;5;246;03m// Variables are declared with the `var` keyword. JavaScript is dynamically[39;00m [38;5;246;03m// typed, so you don't need to specify type. Assignment uses a single `=`[39;00m [38;5;246;03m// character.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252msomeVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m [38;5;246;03m// If you leave the var keyword off, you won't get an error...[39;00m [38;5;252msomeOtherVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m [38;5;246;03m// ...but your variable will be created in the global scope, not in the scope[39;00m [38;5;246;03m// you defined it in.[39;00m [38;5;246;03m// Variables declared without being assigned to are set to undefined.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252msomeThirdVar[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = undefined[39;00m [38;5;246;03m// If you want to declare a couple of variables, then you could use a comma[39;00m [38;5;246;03m// separator[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252msomeFourthVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252msomeFifthVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m4[39m[38;5;252m;[39m [38;5;246;03m// There's shorthand for performing math operations on variables:[39;00m [38;5;252msomeVar[39m[38;5;252m [39m[38;5;252m+=[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// equivalent to someVar = someVar + 5; someVar is 10 now[39;00m [38;5;252msomeVar[39m[38;5;252m [39m[38;5;252m*=[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// now someVar is 100[39;00m [38;5;246;03m// and an even-shorter-hand for adding or subtracting 1[39;00m [38;5;252msomeVar[39m[38;5;252m++[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// now someVar is 101[39;00m [38;5;252msomeVar[39m[38;5;252m--[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// back to 100[39;00m [38;5;246;03m// Arrays are ordered lists of values, of any type.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyArray[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m[[39m[38;5;214m"Hello"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m45[39m[38;5;252m,[39m[38;5;252m [39m[38;5;70;01mtrue[39;00m[38;5;252m][39m[38;5;252m;[39m [38;5;246;03m// Their members can be accessed using the square-brackets subscript syntax.[39;00m [38;5;246;03m// Array indices start at zero.[39;00m [38;5;252mmyArray[39m[38;5;252m[[39m[38;5;67m1[39m[38;5;252m][39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 45[39;00m [38;5;246;03m// Arrays are mutable and of variable length.[39;00m [38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252mpush[39m[38;5;252m([39m[38;5;214m"World"[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252mlength[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 4[39;00m [38;5;246;03m// Add/Modify at specific index[39;00m [38;5;252mmyArray[39m[38;5;252m[[39m[38;5;67m3[39m[38;5;252m][39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m"Hello"[39m[38;5;252m;[39m [38;5;246;03m// Add and remove element from front or back end of an array[39;00m [38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252munshift[39m[38;5;252m([39m[38;5;67m3[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// Add as the first element[39;00m [38;5;252msomeVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252mshift[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// Remove first element and return it[39;00m [38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252mpush[39m[38;5;252m([39m[38;5;67m3[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// Add as the last element[39;00m [38;5;252msomeVar[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mmyArray[39m[38;5;252m.[39m[38;5;252mpop[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// Remove last element and return it[39;00m [38;5;246;03m// Join all elements of an array with semicolon[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyArray0[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m[[39m[38;5;67m32[39m[38;5;252m,[39m[38;5;70;01mfalse[39;00m[38;5;252m,[39m[38;5;214m"js"[39m[38;5;252m,[39m[38;5;67m12[39m[38;5;252m,[39m[38;5;67m56[39m[38;5;252m,[39m[38;5;67m90[39m[38;5;252m][39m[38;5;252m;[39m [38;5;252mmyArray0[39m[38;5;252m.[39m[38;5;252mjoin[39m[38;5;252m([39m[38;5;214m";"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "32;false;js;12;56;90"[39;00m [38;5;246;03m// Get subarray of elements from index 1 (include) to 4 (exclude)[39;00m [38;5;252mmyArray0[39m[38;5;252m.[39m[38;5;252mslice[39m[38;5;252m([39m[38;5;67m1[39m[38;5;252m,[39m[38;5;67m4[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = [false,"js",12][39;00m [38;5;246;03m// Remove 4 elements starting from index 2, and insert there strings[39;00m [38;5;246;03m// "hi","wr" and "ld"; return removed subarray[39;00m [38;5;252mmyArray0[39m[38;5;252m.[39m[38;5;252msplice[39m[38;5;252m([39m[38;5;67m2[39m[38;5;252m,[39m[38;5;67m4[39m[38;5;252m,[39m[38;5;214m"hi"[39m[38;5;252m,[39m[38;5;214m"wr"[39m[38;5;252m,[39m[38;5;214m"ld"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = ["js",12,56,90][39;00m [38;5;246;03m// myArray0 === [32,false,"hi","wr","ld"][39;00m [38;5;246;03m// JavaScript's objects are equivalent to "dictionaries" or "maps" in other[39;00m [38;5;246;03m// languages: an unordered collection of key-value pairs.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m[38;5;252mkey1[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m"Hello"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252mkey2[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m"World"[39m[38;5;252m}[39m[38;5;252m;[39m [38;5;246;03m// Keys are strings, but quotes aren't required if they're a valid[39;00m [38;5;246;03m// JavaScript identifier. Values can be any type.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m[38;5;252mmyKey[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m"myValue"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m"my other key"[39m[38;5;252m:[39m[38;5;252m [39m[38;5;67m4[39m[38;5;252m}[39m[38;5;252m;[39m [38;5;246;03m// Object attributes can also be accessed using the subscript syntax,[39;00m [38;5;252mmyObj[39m[38;5;252m[[39m[38;5;214m"my other key"[39m[38;5;252m][39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 4[39;00m [38;5;246;03m// ... or using the dot syntax, provided the key is a valid identifier.[39;00m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyKey[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "myValue"[39;00m [38;5;246;03m// Objects are mutable; values can be changed and new keys added.[39;00m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyThirdKey[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mtrue[39;00m[38;5;252m;[39m [38;5;246;03m// If you try to access a value that's not yet set, you'll get undefined.[39;00m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyFourthKey[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = undefined[39;00m [38;5;246;03m///////////////////////////////////[39;00m [38;5;246;03m// 3. Logic and Control Structures[39;00m [38;5;246;03m// The `if` structure works as you'd expect.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mcount[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m1[39m[38;5;252m;[39m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mcount[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;67m3[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// evaluated if count is 3[39;00m [38;5;252m}[39m[38;5;252m [39m[38;5;70;01melse[39;00m[38;5;252m [39m[38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mcount[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;67m4[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// evaluated if count is 4[39;00m [38;5;252m}[39m[38;5;252m [39m[38;5;70;01melse[39;00m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// evaluated if it's not either 3 or 4[39;00m [38;5;252m}[39m [38;5;246;03m// As does `while`.[39;00m [38;5;70;01mwhile[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mtrue[39;00m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// An infinite loop![39;00m [38;5;252m}[39m [38;5;246;03m// Do-while loops are like while loops, except they always run at least once.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252minput[39m[38;5;252m;[39m [38;5;70;01mdo[39;00m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252minput[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mgetInput[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m [39m[38;5;70;01mwhile[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252m![39m[38;5;252misValid[39m[38;5;252m([39m[38;5;252minput[39m[38;5;252m)[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;246;03m// The `for` loop is the same as C and Java:[39;00m [38;5;246;03m// initialization; continue condition; iteration.[39;00m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m0[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m<[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mi[39m[38;5;252m++[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// will run 5 times[39;00m [38;5;252m}[39m [38;5;246;03m// Breaking out of labeled loops is similar to Java[39;00m [38;5;252mouter[39m[38;5;252m:[39m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m0[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m<[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mi[39m[38;5;252m++[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m0[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mj[39m[38;5;252m [39m[38;5;252m<[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252mj[39m[38;5;252m++[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m [39m[38;5;252m&&[39m[38;5;252m [39m[38;5;252mj[39m[38;5;252m [39m[38;5;252m==[39m[38;5;67m5[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mbreak[39;00m[38;5;252m [39m[38;5;252mouter[39m[38;5;252m;[39m [38;5;252m [39m[38;5;246;03m// breaks out of outer loop instead of only the inner one[39;00m [38;5;252m [39m[38;5;252m}[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m [38;5;246;03m// The for/in statement allows iteration over properties of an object.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mdescription[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m""[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mperson[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m[38;5;252mfname[39m[38;5;252m:[39m[38;5;214m"Paul"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252mlname[39m[38;5;252m:[39m[38;5;214m"Ken"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252mage[39m[38;5;252m:[39m[38;5;67m18[39m[38;5;252m}[39m[38;5;252m;[39m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mx[39m[38;5;252m [39m[38;5;70;01min[39;00m[38;5;252m [39m[38;5;252mperson[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mdescription[39m[38;5;252m [39m[38;5;252m+=[39m[38;5;252m [39m[38;5;252mperson[39m[38;5;252m[[39m[38;5;252mx[39m[38;5;252m][39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;214m" "[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m [39m[38;5;246;03m// description = 'Paul Ken 18 '[39;00m [38;5;246;03m// The for/of statement allows iteration over iterable objects (including the built-in String, [39;00m [38;5;246;03m// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, [39;00m [38;5;246;03m// and user-defined iterables).[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyPets[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m""[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mpets[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m[[39m[38;5;214m"cat"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m"dog"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m"hamster"[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m"hedgehog"[39m[38;5;252m][39m[38;5;252m;[39m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mpet[39m[38;5;252m [39m[38;5;70;01mof[39;00m[38;5;252m [39m[38;5;252mpets[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyPets[39m[38;5;252m [39m[38;5;252m+=[39m[38;5;252m [39m[38;5;252mpet[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;214m" "[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m [39m[38;5;246;03m// myPets = 'cat dog hamster hedgehog '[39;00m [38;5;246;03m// && is logical and, || is logical or[39;00m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mhouse[39m[38;5;252m.[39m[38;5;252msize[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;214m"big"[39m[38;5;252m [39m[38;5;252m&&[39m[38;5;252m [39m[38;5;252mhouse[39m[38;5;252m.[39m[38;5;252mcolour[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;214m"blue"[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mhouse[39m[38;5;252m.[39m[38;5;252mcontains[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m"bear"[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mcolour[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;214m"red"[39m[38;5;252m [39m[38;5;252m||[39m[38;5;252m [39m[38;5;252mcolour[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;214m"blue"[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// colour is either red or blue[39;00m [38;5;252m}[39m [38;5;246;03m// && and || "short circuit", which is useful for setting default values.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mname[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252motherName[39m[38;5;252m [39m[38;5;252m||[39m[38;5;252m [39m[38;5;214m"default"[39m[38;5;252m;[39m [38;5;246;03m// The `switch` statement checks for equality with `===`.[39;00m [38;5;246;03m// Use 'break' after each case[39;00m [38;5;246;03m// or the cases after the correct one will be executed too.[39;00m [38;5;252mgrade[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m'B'[39m[38;5;252m;[39m [38;5;70;01mswitch[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mgrade[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mcase[39;00m[38;5;252m [39m[38;5;214m'A'[39m[38;5;252m:[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;214m"Great job"[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mbreak[39;00m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mcase[39;00m[38;5;252m [39m[38;5;214m'B'[39m[38;5;252m:[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;214m"OK job"[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mbreak[39;00m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mcase[39;00m[38;5;252m [39m[38;5;214m'C'[39m[38;5;252m:[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;214m"You can do better"[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mbreak[39;00m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mdefault[39;00m[38;5;252m:[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;214m"Oy vey"[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;70;01mbreak[39;00m[38;5;252m;[39m [38;5;252m}[39m [38;5;246;03m///////////////////////////////////[39;00m [38;5;246;03m// 4. Functions, Scope and Closures[39;00m [38;5;246;03m// JavaScript functions are declared with the `function` keyword.[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252mmyFunction[39m[38;5;252m([39m[38;5;252mthing[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;252mthing[39m[38;5;252m.[39m[38;5;252mtoUpperCase[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;252mmyFunction[39m[38;5;252m([39m[38;5;214m"foo"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "FOO"[39;00m [38;5;246;03m// Note that the value to be returned must start on the same line as the[39;00m [38;5;246;03m// `return` keyword, otherwise you'll always return `undefined` due to[39;00m [38;5;246;03m// automatic semicolon insertion. Watch out for this when using Allman style.[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252mmyFunction[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;246;03m// <- semicolon automatically inserted here[39;00m [38;5;252m [39m[38;5;252m{[39m[38;5;252mthisIsAn[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m'object literal'[39m[38;5;252m}[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;252mmyFunction[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = undefined[39;00m [38;5;246;03m// JavaScript functions are first class objects, so they can be reassigned to[39;00m [38;5;246;03m// different variable names and passed to other functions as arguments - for[39;00m [38;5;246;03m// example, when supplying an event handler:[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252mmyFunction[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// this code will be called in 5 seconds' time[39;00m [38;5;252m}[39m [38;5;252msetTimeout[39m[38;5;252m([39m[38;5;252mmyFunction[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m5000[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;246;03m// Note: setTimeout isn't part of the JS language, but is provided by browsers[39;00m [38;5;246;03m// and Node.js.[39;00m [38;5;246;03m// Another function provided by browsers is setInterval[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252mmyFunction[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// this code will be called every 5 seconds[39;00m [38;5;252m}[39m [38;5;252msetInterval[39m[38;5;252m([39m[38;5;252mmyFunction[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m5000[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;246;03m// Function objects don't even have to be declared with a name - you can write[39;00m [38;5;246;03m// an anonymous function definition directly into the arguments of another.[39;00m [38;5;252msetTimeout[39m[38;5;252m([39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// this code will be called in 5 seconds' time[39;00m [38;5;252m}[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m5000[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;246;03m// JavaScript has function scope; functions get their own scope but other blocks[39;00m [38;5;246;03m// do not.[39;00m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mtrue[39;00m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mi[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;252mi[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 5 - not undefined as you'd expect in a block-scoped language[39;00m [38;5;246;03m// This has led to a common pattern of "immediately-executing anonymous[39;00m [38;5;246;03m// functions", which prevent temporary variables from leaking into the global[39;00m [38;5;246;03m// scope.[39;00m [38;5;252m([39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mtemporary[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m [38;5;252m [39m[38;5;246;03m// We can access the global scope by assigning to the "global object", which[39;00m [38;5;252m [39m[38;5;246;03m// in a web browser is always `window`. The global object may have a[39;00m [38;5;252m [39m[38;5;246;03m// different name in non-browser environments such as Node.js.[39;00m [38;5;252m [39m[38;5;31mwindow[39m[38;5;252m.[39m[38;5;252mpermanent[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m10[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m)[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mtemporary[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// raises ReferenceError[39;00m [38;5;252mpermanent[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 10[39;00m [38;5;246;03m// One of JavaScript's most powerful features is closures. If a function is[39;00m [38;5;246;03m// defined inside another function, the inner function has access to all the[39;00m [38;5;246;03m// outer function's variables, even after the outer function exits.[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252msayHelloInFiveSeconds[39m[38;5;252m([39m[38;5;252mname[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mprompt[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m"Hello, "[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252mname[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;214m"!"[39m[38;5;252m;[39m [38;5;252m [39m[38;5;246;03m// Inner functions are put in the local scope by default, as if they were[39;00m [38;5;252m [39m[38;5;246;03m// declared with `var`.[39;00m [38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252minner[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252malert[39m[38;5;252m([39m[38;5;252mprompt[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m [39m[38;5;252msetTimeout[39m[38;5;252m([39m[38;5;252minner[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m5000[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;246;03m// setTimeout is asynchronous, so the sayHelloInFiveSeconds function will[39;00m [38;5;252m [39m[38;5;246;03m// exit immediately, and setTimeout will call inner afterwards. However,[39;00m [38;5;252m [39m[38;5;246;03m// because inner is "closed over" sayHelloInFiveSeconds, inner still has[39;00m [38;5;252m [39m[38;5;246;03m// access to the `prompt` variable when it is finally called.[39;00m [38;5;252m}[39m [38;5;252msayHelloInFiveSeconds[39m[38;5;252m([39m[38;5;214m"Adam"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// will open a popup with "Hello, Adam!" in 5s[39;00m [38;5;246;03m///////////////////////////////////[39;00m [38;5;246;03m// 5. More about Objects; Constructors and Prototypes[39;00m [38;5;246;03m// Objects can contain functions.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyFunc[39m[38;5;252m:[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;214m"Hello world!"[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyFunc[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello world!"[39;00m [38;5;246;03m// When functions attached to an object are called, they can access the object[39;00m [38;5;246;03m// they're attached to using the `this` keyword.[39;00m [38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyString[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m"Hello world!"[39m[38;5;252m,[39m [38;5;252m [39m[38;5;252mmyFunc[39m[38;5;252m:[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyString[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyFunc[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello world!"[39;00m [38;5;246;03m// What this is set to has to do with how the function is called, not where[39;00m [38;5;246;03m// it's defined. So, our function doesn't work if it isn't called in the[39;00m [38;5;246;03m// context of the object.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyFunc[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyFunc[39m[38;5;252m;[39m [38;5;252mmyFunc[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = undefined[39;00m [38;5;246;03m// Inversely, a function can be assigned to the object and gain access to it[39;00m [38;5;246;03m// through `this`, even if it wasn't attached when it was defined.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyOtherFunc[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyString[39m[38;5;252m.[39m[38;5;252mtoUpperCase[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyOtherFunc[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mmyOtherFunc[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyOtherFunc[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "HELLO WORLD!"[39;00m [38;5;246;03m// We can also specify a context for a function to execute in when we invoke it[39;00m [38;5;246;03m// using `call` or `apply`.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252manotherFunc[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252ms[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyString[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252ms[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252manotherFunc[39m[38;5;252m.[39m[38;5;252mcall[39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m,[39m[38;5;252m [39m[38;5;214m" And Hello Moon!"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello World! And Hello Moon!"[39;00m [38;5;246;03m// The `apply` function is nearly identical, but takes an array for an argument[39;00m [38;5;246;03m// list.[39;00m [38;5;252manotherFunc[39m[38;5;252m.[39m[38;5;252mapply[39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252m[[39m[38;5;214m" And Hello Sun!"[39m[38;5;252m][39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello World! And Hello Sun!"[39;00m [38;5;246;03m// This is useful when working with a function that accepts a sequence of[39;00m [38;5;246;03m// arguments and you want to pass an array.[39;00m [38;5;31mMath[39m[38;5;252m.[39m[38;5;252mmin[39m[38;5;252m([39m[38;5;67m42[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m6[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m27[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 6[39;00m [38;5;31mMath[39m[38;5;252m.[39m[38;5;252mmin[39m[38;5;252m([39m[38;5;252m[[39m[38;5;67m42[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m6[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m27[39m[38;5;252m][39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = NaN (uh-oh!)[39;00m [38;5;31mMath[39m[38;5;252m.[39m[38;5;252mmin[39m[38;5;252m.[39m[38;5;252mapply[39m[38;5;252m([39m[38;5;31mMath[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252m[[39m[38;5;67m42[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m6[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m27[39m[38;5;252m][39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 6[39;00m [38;5;246;03m// But, `call` and `apply` are only temporary. When we want it to stick, we can[39;00m [38;5;246;03m// use `bind`.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mboundFunc[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252manotherFunc[39m[38;5;252m.[39m[38;5;252mbind[39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mboundFunc[39m[38;5;252m([39m[38;5;214m" And Hello Saturn!"[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "Hello World! And Hello Saturn!"[39;00m [38;5;246;03m// `bind` can also be used to partially apply (curry) a function.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mproduct[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252ma[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252mb[39m[38;5;252m)[39m[38;5;252m{[39m[38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;252ma[39m[38;5;252m [39m[38;5;252m*[39m[38;5;252m [39m[38;5;252mb[39m[38;5;252m;[39m[38;5;252m [39m[38;5;252m}[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mdoubler[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mproduct[39m[38;5;252m.[39m[38;5;252mbind[39m[38;5;252m([39m[38;5;70;01mthis[39;00m[38;5;252m,[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mdoubler[39m[38;5;252m([39m[38;5;67m8[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 16[39;00m [38;5;246;03m// When you call a function with the `new` keyword, a new object is created, and[39;00m [38;5;246;03m// made available to the function via the `this` keyword. Functions designed to be[39;00m [38;5;246;03m// called like that are called constructors.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mMyConstructor[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyNumber[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyNewObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mnew[39;00m[38;5;252m [39m[38;5;252mMyConstructor[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = {myNumber: 5}[39;00m [38;5;252mmyNewObj[39m[38;5;252m.[39m[38;5;252mmyNumber[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 5[39;00m [38;5;246;03m// Unlike most other popular object-oriented languages, JavaScript has no[39;00m [38;5;246;03m// concept of 'instances' created from 'class' blueprints; instead, JavaScript[39;00m [38;5;246;03m// combines instantiation and inheritance into a single concept: a 'prototype'.[39;00m [38;5;246;03m// Every JavaScript object has a 'prototype'. When you go to access a property[39;00m [38;5;246;03m// on an object that doesn't exist on the actual object, the interpreter will[39;00m [38;5;246;03m// look at its prototype.[39;00m [38;5;246;03m// Some JS implementations let you access an object's prototype on the magic[39;00m [38;5;246;03m// property `__proto__`. While this is useful for explaining prototypes it's not[39;00m [38;5;246;03m// part of the standard; we'll get to standard ways of using prototypes later.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyString[39m[38;5;252m:[39m[38;5;252m [39m[38;5;214m"Hello world!"[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyPrototype[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmeaningOfLife[39m[38;5;252m:[39m[38;5;252m [39m[38;5;67m42[39m[38;5;252m,[39m [38;5;252m [39m[38;5;252mmyFunc[39m[38;5;252m:[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyString[39m[38;5;252m.[39m[38;5;252mtoLowerCase[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252m__proto__[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mmyPrototype[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmeaningOfLife[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 42[39;00m [38;5;246;03m// This works for functions, too.[39;00m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyFunc[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "hello world!"[39;00m [38;5;246;03m// Of course, if your property isn't on your prototype, the prototype's[39;00m [38;5;246;03m// prototype is searched, and so on.[39;00m [38;5;252mmyPrototype[39m[38;5;252m.[39m[38;5;252m__proto__[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyBoolean[39m[38;5;252m:[39m[38;5;252m [39m[38;5;70;01mtrue[39;00m [38;5;252m}[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmyBoolean[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// There's no copying involved here; each object stores a reference to its[39;00m [38;5;246;03m// prototype. This means we can alter the prototype and our changes will be[39;00m [38;5;246;03m// reflected everywhere.[39;00m [38;5;252mmyPrototype[39m[38;5;252m.[39m[38;5;252mmeaningOfLife[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m43[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmeaningOfLife[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 43[39;00m [38;5;246;03m// The for/in statement allows iteration over properties of an object,[39;00m [38;5;246;03m// walking up the prototype chain until it sees a null prototype.[39;00m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mx[39m[38;5;252m [39m[38;5;70;01min[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m[[39m[38;5;252mx[39m[38;5;252m][39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;246;03m///prints:[39;00m [38;5;246;03m// Hello world![39;00m [38;5;246;03m// 43[39;00m [38;5;246;03m// [Function: myFunc][39;00m [38;5;246;03m// true[39;00m [38;5;246;03m// To only consider properties attached to the object itself[39;00m [38;5;246;03m// and not its prototypes, use the `hasOwnProperty()` check.[39;00m [38;5;70;01mfor[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mx[39m[38;5;252m [39m[38;5;70;01min[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mhasOwnProperty[39m[38;5;252m([39m[38;5;252mx[39m[38;5;252m)[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mconsole[39m[38;5;252m.[39m[38;5;252mlog[39m[38;5;252m([39m[38;5;252mmyObj[39m[38;5;252m[[39m[38;5;252mx[39m[38;5;252m][39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m [38;5;246;03m///prints:[39;00m [38;5;246;03m// Hello world![39;00m [38;5;246;03m// We mentioned that `__proto__` was non-standard, and there's no standard way to[39;00m [38;5;246;03m// change the prototype of an existing object. However, there are two ways to[39;00m [38;5;246;03m// create a new object with a given prototype.[39;00m [38;5;246;03m// The first is Object.create, which is a recent addition to JS, and therefore[39;00m [38;5;246;03m// not available in all implementations yet.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;31mObject[39m[38;5;252m.[39m[38;5;252mcreate[39m[38;5;252m([39m[38;5;252mmyPrototype[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mmyObj[39m[38;5;252m.[39m[38;5;252mmeaningOfLife[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 43[39;00m [38;5;246;03m// The second way, which works anywhere, has to do with constructors.[39;00m [38;5;246;03m// Constructors have a property called prototype. This is *not* the prototype of[39;00m [38;5;246;03m// the constructor function itself; instead, it's the prototype that new objects[39;00m [38;5;246;03m// are given when they're created with that constructor and the new keyword.[39;00m [38;5;252mMyConstructor[39m[38;5;252m.[39m[38;5;252mprototype[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;252mmyNumber[39m[38;5;252m:[39m[38;5;252m [39m[38;5;67m5[39m[38;5;252m,[39m [38;5;252m [39m[38;5;252mgetMyNumber[39m[38;5;252m:[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mmyNumber[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyNewObj2[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mnew[39;00m[38;5;252m [39m[38;5;252mMyConstructor[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mmyNewObj2[39m[38;5;252m.[39m[38;5;252mgetMyNumber[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 5[39;00m [38;5;252mmyNewObj2[39m[38;5;252m.[39m[38;5;252mmyNumber[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m6[39m[38;5;252m;[39m [38;5;252mmyNewObj2[39m[38;5;252m.[39m[38;5;252mgetMyNumber[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 6[39;00m [38;5;246;03m// Built-in types like strings and numbers also have constructors that create[39;00m [38;5;246;03m// equivalent wrapper objects.[39;00m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyNumber[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m12[39m[38;5;252m;[39m [38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mmyNumberObj[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mnew[39;00m[38;5;252m [39m[38;5;31mNumber[39m[38;5;252m([39m[38;5;67m12[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252mmyNumber[39m[38;5;252m [39m[38;5;252m==[39m[38;5;252m [39m[38;5;252mmyNumberObj[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = true[39;00m [38;5;246;03m// Except, they aren't exactly equivalent.[39;00m [38;5;70;01mtypeof[39;00m[38;5;252m [39m[38;5;252mmyNumber[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 'number'[39;00m [38;5;70;01mtypeof[39;00m[38;5;252m [39m[38;5;252mmyNumberObj[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = 'object'[39;00m [38;5;252mmyNumber[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;252mmyNumberObj[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = false[39;00m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;67m0[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// This code won't execute, because 0 is falsy.[39;00m [38;5;252m}[39m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;70;01mnew[39;00m[38;5;252m [39m[38;5;31mNumber[39m[38;5;252m([39m[38;5;67m0[39m[38;5;252m)[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// This code will execute, because wrapped numbers are objects, and objects[39;00m [38;5;252m [39m[38;5;246;03m// are always truthy.[39;00m [38;5;252m}[39m [38;5;246;03m// However, the wrapper objects and the regular builtins share a prototype, so[39;00m [38;5;246;03m// you can actually add functionality to a string, for instance.[39;00m [38;5;31mString[39m[38;5;252m.[39m[38;5;252mprototype[39m[38;5;252m.[39m[38;5;252mfirstCharacter[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mthis[39;00m[38;5;252m.[39m[38;5;252mcharAt[39m[38;5;252m([39m[38;5;67m0[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;214m"abc"[39m[38;5;252m.[39m[38;5;252mfirstCharacter[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// = "a"[39;00m [38;5;246;03m// This fact is often used in "polyfilling", which is implementing newer[39;00m [38;5;246;03m// features of JavaScript in an older subset of JavaScript, so that they can be[39;00m [38;5;246;03m// used in older environments such as outdated browsers.[39;00m [38;5;246;03m// For instance, we mentioned that Object.create isn't yet available in all[39;00m [38;5;246;03m// implementations, but we can still use it with this polyfill:[39;00m [38;5;70;01mif[39;00m[38;5;252m [39m[38;5;252m([39m[38;5;31mObject[39m[38;5;252m.[39m[38;5;252mcreate[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;70;01mundefined[39;00m[38;5;252m)[39m[38;5;252m{[39m[38;5;252m [39m[38;5;246;03m// don't overwrite it if it exists[39;00m [38;5;252m [39m[38;5;31mObject[39m[38;5;252m.[39m[38;5;252mcreate[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252mproto[39m[38;5;252m)[39m[38;5;252m{[39m [38;5;252m [39m[38;5;246;03m// make a temporary constructor with the right prototype[39;00m [38;5;252m [39m[38;5;70;01mvar[39;00m[38;5;252m [39m[38;5;252mConstructor[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;70;01mfunction[39;00m[38;5;252m([39m[38;5;252m)[39m[38;5;252m{[39m[38;5;252m}[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252mConstructor[39m[38;5;252m.[39m[38;5;252mprototype[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252mproto[39m[38;5;252m;[39m [38;5;252m [39m[38;5;246;03m// then use it to create a new, appropriately-prototyped object[39;00m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;70;01mnew[39;00m[38;5;252m [39m[38;5;252mConstructor[39m[38;5;252m([39m[38;5;252m)[39m[38;5;252m;[39m [38;5;252m [39m[38;5;252m}[39m[38;5;252m;[39m [38;5;252m}[39m [38;5;246;03m// ES6 Additions[39;00m [38;5;246;03m// The "let" keyword allows you to define variables in a lexical scope, [39;00m [38;5;246;03m// as opposed to a block scope like the var keyword does.[39;00m [38;5;70;01mlet[39;00m[38;5;252m [39m[38;5;252mname[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m"Billy"[39m[38;5;252m;[39m [38;5;246;03m// Variables defined with let can be reassigned new values.[39;00m [38;5;252mname[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;214m"William"[39m[38;5;252m;[39m [38;5;246;03m// The "const" keyword allows you to define a variable in a lexical scope[39;00m [38;5;246;03m// like with let, but you cannot reassign the value once one has been assigned.[39;00m [38;5;70;01mconst[39;00m[38;5;252m [39m[38;5;252mpi[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m3.14[39m[38;5;252m;[39m [38;5;252mpi[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;67m4.13[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// You cannot do this.[39;00m [38;5;246;03m// There is a new syntax for functions in ES6 known as "lambda syntax".[39;00m [38;5;246;03m// This allows functions to be defined in a lexical scope like with variables[39;00m [38;5;246;03m// defined by const and let. [39;00m [38;5;70;01mconst[39;00m[38;5;252m [39m[38;5;252misEven[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m([39m[38;5;252mnumber[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m=>[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;252mnumber[39m[38;5;252m [39m[38;5;252m%[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;67m0[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;252misEven[39m[38;5;252m([39m[38;5;67m7[39m[38;5;252m)[39m[38;5;252m;[39m[38;5;252m [39m[38;5;246;03m// false[39;00m [38;5;246;03m// The "equivalent" of this function in the traditional syntax would look like this:[39;00m [38;5;70;01mfunction[39;00m[38;5;252m [39m[38;5;252misEven[39m[38;5;252m([39m[38;5;252mnumber[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;252mnumber[39m[38;5;252m [39m[38;5;252m%[39m[38;5;252m [39m[38;5;67m2[39m[38;5;252m [39m[38;5;252m===[39m[38;5;252m [39m[38;5;67m0[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m [38;5;246;03m// I put the word "equivalent" in double quotes because a function defined[39;00m [38;5;246;03m// using the lambda syntax cannnot be called before the definition.[39;00m [38;5;246;03m// The following is an example of invalid usage:[39;00m [38;5;252madd[39m[38;5;252m([39m[38;5;67m1[39m[38;5;252m,[39m[38;5;252m [39m[38;5;67m8[39m[38;5;252m)[39m[38;5;252m;[39m [38;5;70;01mconst[39;00m[38;5;252m [39m[38;5;252madd[39m[38;5;252m [39m[38;5;252m=[39m[38;5;252m [39m[38;5;252m([39m[38;5;252mfirstNumber[39m[38;5;252m,[39m[38;5;252m [39m[38;5;252msecondNumber[39m[38;5;252m)[39m[38;5;252m [39m[38;5;252m=>[39m[38;5;252m [39m[38;5;252m{[39m [38;5;252m [39m[38;5;70;01mreturn[39;00m[38;5;252m [39m[38;5;252mfirstNumber[39m[38;5;252m [39m[38;5;252m+[39m[38;5;252m [39m[38;5;252msecondNumber[39m[38;5;252m;[39m [38;5;252m}[39m[38;5;252m;[39m