javascript--Closure Package

I. Characteristics of closures and the relationship between closures and garbage collection mechanisms

1<script>2         /**3 * Characteristics of closure structure4 * functions nested functions5 * The nested function has a return value, and the return value calls the variable of the outer function .6          **/7 8 9         /**Ten * Garbage collection mechanism One * Memory is used when variables are created A * Garbage collection mechanism is recycled (removed from memory) by unused variables and exhausted variables -          * */ -  the         functionfn1 () { -             //Local Variables -             vardata1 = "Data"; -             functionfn2 () { +                 returndata1; -             } +             returnfn2; A         } at  -  - //Console.log (FN1 ());//Output FN2 -  -         //This can output the data stored in local variables, indicating that the garbage collection mechanism does not recycle local variables -         //Cons: Consuming memory (local variables not being deleted) in         //benefit: Local variable data1 does not pollute external variables -Console.log (FN1 ());//"Data" to</script>

Two. Examples of non-closures

1<script>2         vararr = [10,20,30];3 4         //The usual for loop I creates within the parentheses of the for5        /*For (var i = 0; i < arr.length; i++) {6 Arr[i] = function () {7 Console.log (i);8           }9 Ten         } One Arr[0] ();//Output 3*/ A  -  -         //This is the equivalent of creating an I variable on the outside, which is used in the For loop. the /*var i = 0; - For (; i < arr.length; i++) { - Arr[i] = function () { - Console.log (i); +             } -  +         }*/ A  at //Arr[0] ();//Output 3 At this moment of execution, ask how much I was - //alert (i);//Output 3 -  -  -         //--------------------Example 2------------------------- -Console.log (111); in         vari = 0; -         //The for loop was executed at the moment we released it. to          for(; i < 3; i++) { +           //The timer actually executes at the last minute of the For loop. -SetTimeout (function () { theConsole.log (i);//Output 3 *},1000); $         }Panax Notoginseng  -Console.log (222); the</script>

Three. Examples of differences between closures and non-closures

1<script>2         //does not form a closure, the function inside does not use the external function variable3  /*var name = "The window";4 var object = {5 Name: "My Object",6 getnamefunc:function () {7 Console.log (this);//Get Object8 return function () {9 //What is this here?Ten Console.log (this);//At the moment the call becomes window One return this.name; A                 } -             } -         }; the  - Console.log (Object.getnamefunc ()); - //Object.getnamefunc () run to get function*/ -  + //form a closure, the function inside uses the external function variable -  varName = "the window"; +  varObject = { AName: "My Object", atGetnamefunc:function () { -          //Save the external this to the local variable. -         varthat = This; -          return function () { -              //a local variable was called by a nested function, which forms a closure, -              //so that variable is not recycled and keeps the outside object.  in              returnThat.name; -          } to      } +  }; -  the Console.log (Object.getnamefunc ()); *</script>

javascript--Closure Package