forEach是javascript中遍历数组的要领,大部分人经常运用for()轮回来遍历数组,如今我们来看一下forEach的用法。
兼容性
Firefox 和Chrome 的Array 范例都有forEach的函数。运用以下:
<script>
var arryAll = [];
arryAll.push(1);
arryAll.push(2);
arryAll.push(3);
arryAll.push(4);
arryAll.forEach(function(e){
alert(e);
})
</script>
然则在IE中却没有forEach这个要领 :alert(Array.prototype.forEach); //undefined
然则我们能够运用以下要领来让IE兼容这个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++;
}
};
}
通常有轮回的处所,都邑涉及到跳出轮回的状态,那末forEach怎样跳出轮回呢?
Js此种状态的forEach不能运用continue, break;能够运用以下两种体式格局:
if 语句掌握
return (return true/return false) return –> 相似continue
例子:掏出数组中3的倍数和7的倍数的数
<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(7);
arryAll.push(21);
arryAll.push(22);
arryAll.push(28);
var arrySpecial = [];
arryAll.forEach(function(e){
if(e%2==0)
{
arrySpecial.push(e);
}else if(e%3==0)
{
arrySpecial.push(e);
}
})
</script>