Javascript 数组循环遍历之forEach
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[-]2. forEach 函数。
Firefox 和Chrome 的Array 类型都有forEach的函数。使用如下:
3. 让IE兼容forEach方法
4. 如何跳出循环?
Js 此种状况的forEach 不能使用continue, break; 可以使用如下两种方式:
1. if 语句控制
2. return . (return true, false)
return --> 类似continue
以下例子是取出数组中2的倍数和3的倍数的数;
使用return 达到以上效果
- js 数组循环遍历
- forEach 函数
- 让IE兼容forEach方法
- 如何跳出循环
1. js 数组循环遍历。
数组循环变量,最先想到的就是 for(var i=0;i<count;i++)这样的方式了。除此之外,也可以使用较简便的forEach 方式
2. forEach 函数。
Firefox 和Chrome 的Array 类型都有forEach的函数。使用如下:- <!--Add by oscar999-->
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
- <HTML>
- <HEAD>
- <TITLE> New Document </TITLE>
- <META NAME="Author" CONTENT="oscar999">
- </HEAD>
- <BODY>
- <script>
- var arryAll = [];
- arryAll.push(1);
- arryAll.push(2);
- arryAll.push(3);
- arryAll.push(4);
- arryAll.forEach(function(e){
- alert(e);
- })
- </script>
- </BODY>
- </HTML>
<!--Add by oscar999--><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML><HEAD><TITLE> New Document </TITLE><META NAME="Author" CONTENT="oscar999"></HEAD><BODY><script>var arryAll = [];arryAll.push(1);arryAll.push(2);arryAll.push(3);arryAll.push(4);arryAll.forEach(function(e){alert(e);})</script></BODY></HTML>
但是以上,代码在IE中却无法正常工作。
因为IE的Array 没有这个方法
- alert(Array.prototype.forEach);
alert(Array.prototype.forEach);执行以上这句得到的是 "undefined", 也就是说在IE 中 Array 没有forEach的方法。
3. 让IE兼容forEach方法
既然IE的Array 没哟forEach方法, 我们就给它手动添加这个原型方法。
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEach
- //Array.forEach implementation for IE support..
- //https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEach
- if (!Array.prototype.forEach) {
- Array.prototype.forEach = function(callback, thisArg) {
- var T, k;
- if (this == null) {
- throw new TypeError(" this is null or not defined");
- }
- var O = Object(this);
- var len = O.length >>> 0; // Hack to convert O.length to a UInt32
- if ({}.toString.call(callback) != "[object Function]") {
- throw new TypeError(callback + " is not a function");
- }
- if (thisArg) {
- T = thisArg;
- }
- k = 0;
- while (k < len) {
- var kValue;
- if (k in O) {
- kValue = O[k];
- callback.call(T, kValue, k, O);
- }
- k++;
- }
- };
- }
//Array.forEach implementation for IE support..//https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEachif (!Array.prototype.forEach) {Array.prototype.forEach = function(callback, thisArg) {var T, k;if (this == null) {throw new TypeError(" this is null or not defined");}var O = Object(this);var len = O.length >>> 0; // Hack to convert O.length to a UInt32if ({}.toString.call(callback) != "[object Function]") {throw new TypeError(callback + " is not a function");}if (thisArg) {T = thisArg;}k = 0;while (k < len) {var kValue;if (k in O) {kValue = O[k];callback.call(T, kValue, k, O);}k++;}};}详细介绍可以参照:
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEach
4. 如何跳出循环?
Js 此种状况的forEach 不能使用continue, break; 可以使用如下两种方式:1. if 语句控制
2. return . (return true, false)
return --> 类似continue
以下例子是取出数组中2的倍数和3的倍数的数;
- <!--Add by oscar999-->
- <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
- <HTML>
- <HEAD>
- <TITLE> New Document </TITLE>
- <META NAME="Author" CONTENT="oscar999">
- </HEAD>
- <BODY>
- <script>
- if (!Array.prototype.forEach) {
- Array.prototype.forEach = function(callback, thisArg) {
- var T, k;
- if (this == null) {
- throw new TypeError(" this is null or not defined");
- }
- var O = Object(this);
- var len = O.length >>> 0; // Hack to convert O.length to a UInt32
- if ({}.toString.call(callback) != "[object Function]") {
- throw new TypeError(callback + " is not a function");
- }
- if (thisArg) {
- T = thisArg;
- }
- k = 0;
- while (k < len) {
- var kValue;
- if (k in O) {
- kValue = O[k];
- callback.call(T, kValue, k, O);
- }
- k++;
- }
- };
- }
- var arryAll = [];
- arryAll.push(1);
- arryAll.push(2);
- arryAll.push(3);
- arryAll.push(4);
- arryAll.push(5);
- var arrySpecial = [];
- arryAll.forEach(function(e){
- if(e%2==0)
- {
- arrySpecial.push(e);
- }else if(e%3==0)
- {
- arrySpecial.push(e);
- }
- })
- </script>
- </BODY>
- </HTML>
<!--Add by oscar999--><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML><HEAD><TITLE> New Document </TITLE><META NAME="Author" CONTENT="oscar999"></HEAD><BODY><script>if (!Array.prototype.forEach) {Array.prototype.forEach = function(callback, thisArg) {var T, k;if (this == null) {throw new TypeError(" this is null or not defined");}var O = Object(this);var len = O.length >>> 0; // Hack to convert O.length to a UInt32if ({}.toString.call(callback) != "[object Function]") {throw new TypeError(callback + " is not a function");}if (thisArg) {T = thisArg;}k = 0;while (k < len) {var kValue;if (k in O) {kValue = O[k];callback.call(T, kValue, k, O);}k++;}};}var arryAll = [];arryAll.push(1);arryAll.push(2);arryAll.push(3);arryAll.push(4);arryAll.push(5);var arrySpecial = [];arryAll.forEach(function(e){if(e%2==0) {arrySpecial.push(e);}else if(e%3==0) {arrySpecial.push(e);}})</script></BODY></HTML>
使用return 达到以上效果
- arryAll.forEach(function(e){
- if(e%2==0)
- {
- arrySpecial.push(e);
- return;
- }
- if(e%3==0)
- {
- arrySpecial.push(e);
- return;
- }
- })
arryAll.forEach(function(e){if(e%2==0) {arrySpecial.push(e);return;}if(e%3==0) { arrySpecial.push(e);return;}})
至于如何写类似break 的效果,目前尚未找到比较好的办法。
有搜索一下,有的说return false 可以达成, 试了一下, 效果和return 和return ture 是一样的。
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