如何提取数组的偶数元素? [英] How do I extract even elements of an Array?

问题描述

var arr = [4, 5, 7, 8, 14, 45, 76];

function even(a) {
  var ar = [];

  for (var i = 0; i < a.length; i++) {
    ar.push(a[2 * i + 1]);
  }

  return ar;
}

alert(even(arr));

http://jsbin.com/unocar/2/edit

为了输出数组的偶数(索引)元素，我尝试了这段代码.它有效，但它也会输出一些空元素.如何修复此代码以仅输出现有元素?

I have tried this code in order to output even (index) elements of an array. It works, but it also outputs some empty elements. How do I fix this code to output only existing elements?

推荐答案

要么使用模数:

for (var i = 0; i < a.length; i++) {
    if(i % 2 === 0) { // index is even
        ar.push(a[i]);
    }
}

或者通过相应地增加 i 来跳过每个第二个元素:

or skip every second element by incrementing i accordingly:

for(var i = 0; i < a.length; i += 2) {  // take every second element
    ar.push(a[i]);
}

注意:您的代码实际上从数组中获取具有奇数 个索引的元素.如果这是你想要的，你必须使用 i % 2 === 1 或分别用 var i = 1 开始循环.

Notice: Your code actually takes the elements with odd indexes from the array. If this is what you want you have to use i % 2 === 1 or start the loop with var i = 1 respectively.

这篇关于如何提取数组的偶数元素?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！