JS Closure Example

vardb =(function () {//Create a hidden object, this object holds some data//This object cannot be accessed from outside.vardata = {};//Create a function that provides some way to access datareturnfunction (key, Val) {if(val = = = undefined) {returnData[key]}//Get    Else{returnData[key] = val}//Set    }//We can call this anonymous method//return this intrinsic function, which is a closed packet}) ();d B ('x');//Back to undefineddb'x',1);//set data[' x '] to 1db'x');//returns 1//We can't access data, the object itself .//but we can set up a member of it

1. When a function is nested within a function, the internal function can access the variables in the external function.

2. External variables (environment variables?) ），

Including:

2.1 Global variables, including DOM.

2.2 Variables or functions for external functions.

If a function accesses its external variables, it is a closed packet.

Technically, in JS, each function is a closure, because it always has access to the data defined outside it.

Closed Package without return:

function Closureexample () {            var;            SetTimeout (function () {                Console.log (+ +temp)            ;  + );        }        Closureexample ()

Closure instances:

  Function Demo () {            var5;            function Add () {                Console.log (temp+ +)            ;            } return add;        }         var demeinstance = demo ();         // the console demeinstance,temp has been added

JS Closure Example