JS array iteration method_javascript skills-JS Tutorial-php.cn

JS array iteration method_javascript skills

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Release： 2016-05-16 16:15:38

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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

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I hope this article will be helpful to everyone’s JavaScript programming design.