dnk

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(function() {
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  'use strict';
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  // Check to make sure service workers are supported in the current browser,
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  // and that the current page is accessed from a secure origin. Using a
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  // service worker from an insecure origin will trigger JS console errors.
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  var isLocalhost = Boolean(window.location.hostname === 'localhost' ||
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      // [::1] is the IPv6 localhost address.
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      window.location.hostname === '[::1]' ||
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      // 127.0.0.1/8 is considered localhost for IPv4.
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      window.location.hostname.match(
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        /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
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      )
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    );
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  window.addEventListener('load', function() {
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      if ('serviceWorker' in navigator &&
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          (window.location.protocol === 'https:' || isLocalhost)) {
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        navigator.serviceWorker.register('service-worker.js')
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        .then(function(registration) {
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          // updatefound is fired if service-worker.js changes.
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          registration.onupdatefound = function() {
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            // updatefound is also fired the very first time the SW is installed,
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            // and there's no need to prompt for a reload at that point.
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            // So check here to see if the page is already controlled,
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            // i.e. whether there's an existing service worker.
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            if (navigator.serviceWorker.controller) {
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              // The updatefound event implies that registration.installing is set
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              var installingWorker = registration.installing;
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              installingWorker.onstatechange = function() {
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                switch (installingWorker.state) {
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                  case 'installed':
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                    // At this point, the old content will have been purged and the
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                    // fresh content will have been added to the cache.
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                    // It's the perfect time to display a "New content is
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                    // available; please refresh." message in the page's interface.
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                    break;
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                  case 'redundant':
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                    throw new Error('The installing ' +
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                                    'service worker became redundant.');
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                  default:
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                    // Ignore
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                }
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              };
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            }
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          };
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        }).catch(function(e) {
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          console.error('Error during service worker registration:', e);
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        });
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      }
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  });
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})();
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