Closures
a function along with it's outer scope is called closure. Closure is basically a function along with it's lexical scope bundled together is called Closure.
function x() { var a = 7; function y() { console.log(a); } y();}x();closure basically gives you the access of outer function's scope from the inner function.
- when functions are returned they still maintain their lexical scope
function x() { var a = 7; return function y() { console.log(a); };}x();guess the output
value of a ?
function x() { var a = 7; return function y() { console.log(a); }; a = 100; return y;}x();in this case value of a woule be 100;
- module design pattern
- curring
- function like ones (higer order functions)
- memoize
- maiting state in async world
- setTimeouts
- iterators
- data hiding and encluption
data hiding like other functions and peices of code don;t have access to it.
var counter = 0;function incrementCounter() { count++;}
function counter() { var counter = 0; return function incrementCounter() { count++; console.log(count); };}var counter1 = counter();counter1(); //1counter1(); //2var counter2 = counter();counter1(); //1// now it some of from the out side the code will access it it will give errormake a counter
function Conter() { var count = 0; this.incrementCounter = function () { count++; console.log(count); }; this.decrementCounter = function () { count--; console.log(count); };}var counter1 = new Counter();counter1.incrementCounter();counter1.decrementCounter();