javascript closure function example

1A closure gives you access to an outer function’s scope from an inner function
2//example
3function init() {
4  var name = 'Mozilla'; // name is a local variable created by init
5  function displayName() { // displayName() is the inner function, a closure
6    alert(name); // use variable declared in the parent function
7  }
8  displayName();
9}
10init();
11

1function makeFunc() {
2  var name = 'Mozilla';
3  function displayName() {
4    alert(name);
5  }
6  return displayName;
7}
8
9var myFunc = makeFunc();
10myFunc();
11

1var counter = (function() {
2  var privateCounter = 0;
3  function changeBy(val) {
4    privateCounter += val;
5  }
6  return {
7    increment: function() {
8      changeBy(1);
9    },
10    decrement: function() {
11      changeBy(-1);
12    },
13    value: function() {
14      return privateCounter;
15    }
16  };
17})();
18
19console.log(counter.value()); // logs 0
20counter.increment();
21counter.increment();
22console.log(counter.value()); // logs 2
23counter.decrement();
24console.log(counter.value()); // logs 1
25