---
id: 56bbb991ad1ed5201cd392cd
challengeType: 1
videoUrl: 'https://scrimba.com/c/cRbVETW'
forumTopicId: 18238
title: 使用 shift() 操作数组
---

## Description
<section id='description'>
<code>pop()</code>函数用来移出数组中最后一个元素。如果想要移出第一个元素要怎么办呢？
这就是<code>.shift()</code>的用武之地。它的工作原理就像<code>.pop()</code>，但它移除的是第一个元素，而不是最后一个。
</section>

## Instructions
<section id='instructions'>
使用<code>.shift()</code>函数移出<code>myArray</code>中的第一项，并把“移出”的值赋给<code>removedFromMyArray</code>。
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>myArray</code>应该等于<code>[["dog", 3]]</code>。
    testString: assert((function(d){if(d[0][0] == 'dog' && d[0][1] === 3 && d[1] == undefined){return true;}else{return false;}})(myArray));
  - text: <code>removedFromMyArray</code>应该包含<code>["John", 23]</code>。
    testString: assert((function(d){if(d[0] == 'John' && d[1] === 23 && typeof removedFromMyArray === 'object'){return true;}else{return false;}})(removedFromMyArray));

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
// Example
var ourArray = ["Stimpson", "J", ["cat"]];
var removedFromOurArray = ourArray.shift();
// removedFromOurArray now equals "Stimpson" and ourArray now equals ["J", ["cat"]].

// Setup
var myArray = [["John", 23], ["dog", 3]];

// Only change code below this line.
var removedFromMyArray;


```

</div>


### After Test
<div id='js-teardown'>

```js
(function(y, z){return 'myArray = ' + JSON.stringify(y) + ' & removedFromMyArray = ' + JSON.stringify(z);})(myArray, removedFromMyArray);
```

</div>

</section>

## Solution
<section id='solution'>


```js
var myArray = [["John", 23], ["dog", 3]];

// Only change code below this line.
var removedFromMyArray = myArray.shift();
```

</section>