EXTJS uses forin for Array traversal and trap Classification

I. Q: I have the following code in extjs. Can I guess the execution result? Vararr [1, 2, 3]; for (varkinarr) {alert (arr [k]);} 2. Answer: five items will be generated by alert successively: 1, 2, 3, function (B, c) {varathis. length; cc | 0; c + (c & lt; 0 )? A: 0;... I. Q: Is there the following code in extjs? Guess the execution result? Var arr = [1, 2, 3]; for (var k in arr) {alert (arr [k]);} 2. The answer is: five items will be generated by alert successively: 1, 2, 3, function (B, c) {var a = this. length; c = c | 0; c + = (c <0 )? A: 0; for (; c = B) {return c} return-1}, function (B) {var a = this. indexOf (B); if (! =-1) {this. splice (a, 1)} return this} 3. There are two solutions: 1. Use length to traverse: var arr = [1, 2, 3]; var arrLen = arr. length; for (var I = 0; I alert (arr [I]);} 2. Add the judgment condition: var arr = [, 3]; for (var k in arr) {if (arr. hasOwnProperty (k) {alert (arr [k]) ;}} 4. Analysis Reason: Set 0 to 2 alert (arr [k]); change "0" 2 "0" to "0" 2 "alert (k + '0" 2 "0" 2 "0" 2 "+ arr [k]). 0. 2. 0. 2. The value of K is more indexOf and remove than expected. The disadvantages of traversing arrays with for in are exposed again. View the ext-base.js source code you will find ExtJS in JavaScript Array, Date, Function, Number, string and other extensions, the Array Extension code is as follows: Ext. applyIf (Array. prototype, {indexOf: function (B, c) {var a = this. length; c = c | 0; c + = (c <0 )? A: 0; for (; c <a; ++ c) {if (this = B) {return c} return-1}, remove: function (B) {var a = this. indexOf (B); if (! =-1) {this. splice (a, 1)} return this}); Method Description: indexOf: determines whether the specified object exists in the array. If so, the corresponding index is returned, if not,-1 is returned. Remove: deletes a specified object from the array.