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The concept of closures has been very vague, what exactly is closure?
// function nesting functions, intrinsic functions can refer to parameter variables of external functions, parameters and variables are not reclaimed by garbage collection mechanism, because the internal function BBB () refers to the variable of AAA () function aaa (a) { var b = 5; function BBB () { alert (a); Alert (b)}}aaa (); // the garbage collection mechanism in JS function aaa () { var a = 1;} AAA ();// a simple closure example. Decision A is not reclaimed by the garbage collection system function aaa ( ) {var a = 5; function BBB () { alert (a) }//define a global variable A to implement the additive functionvarA = 1;functionaaa () {a++; alert (a); }alert (a); //2alert (a);//3//defines a private variable A that cannot be accumulatedfunctionaaa () {varA = 1; A++; Alert (a)}alert (a);//2alert (a);//2//the benefits of closures, even if a is not a global variable can be accumulatedfunctionaaa () {varA = 1; return function() {a++; Alert (A)}}varc =aaa (); C ();//2C ();//3Alert (a)//I can't find the error .//function declarations and function callsfunctionaaa () {alert (a)}aaa ();//function Expression(functionaaa () {Alert (1)})()//rewrite closures, modular code, reduce pollution from global variablesvarAAA = (function(){ varA = 1;return function() {a++; Alert (A)}) () AAA ()//2AAA ()//3//the existence of private membersvarAAA = (function(){ varA = 1;//Local Variables //BBB (), CCC () Private Method functionBBB () {a++; Alert (a)}functionCCC () {a++; alert (a); } return{b:bbb, C:CCC}}) (); aaa.b ();//2AAA.C ();//3alert (a);//ErrorAlert (BBB);//ErrorAlert (CCC);//Error
//find the index of the corresponding element in the loop<script>varALi = document.getelementbytagname (' li ');//Method 1 for(vari = 0; i<ali.lenght; i++){ (function(i) {Ali[i].onclick=function() {alert (i); }}) (i)}//Method 2 for(vari = 0; i<ali.lenght; i++) {Ali[i].onclick=function(i) {return function() {alert (i); }}) (i)}</script><body><ul><li>111111</li><li>111111</li><li>111111 </li></ul></body>
returnvar c=aaa (); C ()
<script>//memory leak caused by IEvarOdiv = Docudment.getelementbyid (' Div1 ')); Odiv.onclick=function() {Odiv.onclick=function() {alert (odiv.id);};//Workaround OneWindow.onunload =function() {Odiv.onclick=NULL; }}</script><script>//memory leak caused by IEvarOdiv = Docudment.getelementbyid (' Div1 ')); Odiv.onclick=function(){varOdiv =odiv.id; Odiv.onclick=function() {alert (odiv);};//Workaround TwoOdiv =NULL;}</script><body><div id= "Div1" >aaa</div></body>
Closure of the video, found on the internet to speak very well: http://v.youku.com/v_show/id_XNzkwNzM4NTc2.html
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