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JS array iteration method_javascript skills
- WBOYOriginal
- 2016-05-16 16:15:381219browse
The example in this article describes the array iteration method of JS. Share it with everyone for your reference. The specific implementation method is as follows:
<!doctype html>
<html>
<head lang="zh">
<meta charset="utf-8">
<title>js数组迭代</title>
<meta name="renderer" content="webkit">
<script>
var arr1 = [1,2,3,4,5,6];
function double(x){
return 2*x;
}
// map可以产生一个新的数组
// alert(arr1.map(double));
function print(x){
console.log(x*2)
}
arr1.forEach(print);
function even(x){
return x %2 ==0
}
var arr2 = [2,4,,5,6];
// alert(arr2.every(even))//false;
// alert(arr2.some(even))//true;
function add(a,b){
return a*b;
}
var arr3=[1,2,4,5];
var factorial = arr3.reduce(add);
//alert(factorial) //40
var arr4=[1,24,5,6,7,8,234,4];
alert(arr4.filter(even))
</script>
<pre class="brush:php;toolbar:false">
map,filter可以产生一个新的数组
var arr1 = [1,2,3,4,5,6];
function double(x){
return 2*x;
}
//alert(arr1.map(double));
//forEach是对数组每项都调用某个函数，不返回
function print(x){
console.log(x*2)
}
arr1.forEach(print);
//some,every 参数是一个有返回布尔值的函数
function even(x){
return x %2 ==0
}
var arr2 = [2,4,,5,6];
// alert(arr2.every(even))//false;
// alert(arr2.some(even))//true;
//reduce接受一个函数，返回一个值 ，不断累加到最后一项
//同理，reduceRight是由后面累加到第一项，具体可从CONCAT 看出
function add(a,b){
return a*b;
}
var arr3=[1,2,4,5];
var factorial = arr3.reduce(add);
//alert(factorial) //40
//filter与every类似，参入一个返回布尔值 的函数,返回一个新的数组