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// Get page scroll percentage.
function getScrollPercent() {
  return (
    (document.documentElement.scrollTop || document.body.scrollTop) 
    / ( (document.documentElement.scrollHeight || document.body.scrollHeight) 
    - document.documentElement.clientHeight) 
    * 100);
}

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function someFunction(){
  if (true){
    // This variable is defined inside these
    // curly braces, which means its part of the
    // scope of this block and cannot be accessed
    // by other parts of someFunction.
    let blockVariable = 30;
    
    // However, using the 'var' keyword this variable,
    // while defined inside the same block, is part of

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if ('serviceWorker' in navigator) {
  navigator.serviceWorker
    .register('./service-worker.js')
    .then(function() { console.log('Registered service worker!'); });
}

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// This is a function and it defines its own
// local scope. argumentVariable is part of the
// function's scope, as it is an argument in its
// definition.
function parentFunction(argumentVariable){
  // functionVariable and anotherVariable are both
  // part of parentFunction's local scope.
  var functionVariable = 10;
  let anotherVariable = 15;
  

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function user(username, password){
  // Here we use closures to define public functions
  // that can access private variables.
  return {
    getUsername() { return username; },
    setUsername(newUsername) {username = newUsername; },
    checkPassword(givenPassword) { return password == givenPassword; }
  }
}

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var cacheName = 'mockApp-v1.0.0';
var filesToCache = [
  './',
  './index.html',
  './manifest.json',
  './static/js/bundle.js'
];

self.addEventListener('install', function(e) {
  e.waitUntil(caches.open(cacheName)

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// Create a function.
function f(x){
  return x * x;
}
// Use the function.
f(5); // 25

// Create an anonymous function and assign 
// it to a variable.
var g = function(x){

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// This variable is part of the global scope
var globalVariable = 10;

function someFunction(){
  // globalVariable is accessible from someFunction,
  // as it is part of the global scope
  console.log(globalVariable);
}

someFunction(); // Prints 10

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self.addEventListener('activate', function(e) {
  e.waitUntil(caches.keys()
    .then(function(keyList) {
      return Promise.all(keyList.map(function(key) {
        if (key !== cacheName)
          return caches.delete(key);
      }));
  }));
  return self.clients.claim();
});

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// Send a 'GET' request to the specified url and run the callback function when it completes.
function httpGetAsync(url, callback) {
  var xmlHttp = new XMLHttpRequest();
  xmlHttp.onreadystatechange = function() {
    if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
      callback(xmlHttp.responseText);
  };
  xmlHttp.open('GET', url, true);
  xmlHttp.send(null);
}