Simple Application of JavaScript closure, javascript Closure

Simple Application of JavaScript closure, javascript Closure

Closure Definition

In JavaScript, when an internal function is referenced by a variable other than its external function, a closure is formed. In short, closures are functions that can read internal variables of other functions.

Function of closure:

1. Read the internal variables of the function.
2. Keep the values of these variables in the memory.
Simple Application of closures

Example 1:

Function a () {var I = 0; function B () {console. log (++ I);} return B;} var c = a (); // After var c = a () is executed, variable c points to function B, after executing c (), the I value (1) is displayed ). C (); // output 1

Example 2:

(Function () {var I = 0; return function () {console. log (++ I) ;}}) (); // output 1

Example 3:

(Function (I) {return function () {console. log (++ I) ;}}) (0) (); // output 1

Example 4:

For (var I = 0; I <3; I ++) {setTimeout (function (I) {return function () {console. log (I) ;};}) (I), 2000); console. log (I + 10);} // output 10 11 12 (two seconds later) 0 1 2

Example 5:

For (var I = 0; I <3; I ++) {setTimeout (function (I) {return function () {console. log (I) ;};}) (I) (), 2000); console. log (I + 10);} // output 0 10 1 11 2 12 immediately (the program stops running in two seconds)

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