1// closure in javascript
2-> A closure gives you access to an outer function’s scope
3   from an inner function
4
5const outerFun = (a) => {
6  let b = 10;
7  // inner func can use variable/parameter of outer funcion
8  const innerFun = () => {
9    let sum = a + b; 
10    console.log(sum);
11  }
12  return innerFun;
13}
14let inner = outerFun(5);
15inner();

1function outer() {
2  var counter = 0; // Backpack or Closure
3  function incrementCounter() {
4    return counter++;
5  }
6  return incrementCounter;
7}
8
9const count = outer();
10count(); // 0
11count(); // 1
12count(); // 2

1function OuterFunction() {
2
3    var outerVariable = 100;
4
5    function InnerFunction() {
6        alert(outerVariable);
7    }
8
9    return InnerFunction;
10}
11var innerFunc = OuterFunction();

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

1/*A closure is the combination of a function bundled together (enclosed) with references
2to its surrounding state (the lexical environment). In other words, a closure gives you 
3access to an outer function’s scope from an inner function. In JavaScript, closures are 
4created every time a function is created, at function creation time.*/
5
6function init() {
7  var name = 'Mozilla'; // name is a local variable created by init
8  function displayName() { // displayName() is the inner function, a closure
9    alert(name); // use variable declared in the parent function
10  }
11  displayName();
12}
13init();
14

1function OuterFunction() {
2
3    var outerVariable = 1;
4
5    function InnerFunction() {
6        alert(outerVariable);
7    }
8
9    InnerFunction();
10}
11