70 lines
3.0 KiB
Markdown
70 lines
3.0 KiB
Markdown
---
|
|
id: 587d78b2367417b2b2512b0f
|
|
title: Remove Items from an Array with pop() and shift()
|
|
challengeType: 1
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
Both <code>push()</code> and <code>unshift()</code> have corresponding methods that are nearly functional opposites: <code>pop()</code> and <code>shift()</code>. As you may have guessed by now, instead of adding, <code>pop()</code> <em>removes</em> an element from the end of an array, while <code>shift()</code> removes an element from the beginning. The key difference between <code>pop()</code> and <code>shift()</code> and their cousins <code>push()</code> and <code>unshift()</code>, is that neither method takes parameters, and each only allows an array to be modified by a single element at a time.
|
|
Let's take a look:
|
|
<blockquote>let greetings = ['whats up?', 'hello', 'see ya!'];<br><br>greetings.pop();<br>// now equals ['whats up?', 'hello']<br><br>greetings.shift();<br>// now equals ['hello']</blockquote>
|
|
We can also return the value of the removed element with either method like this:
|
|
<blockquote>let popped = greetings.pop();<br>// returns 'hello'<br>// greetings now equals []</blockquote>
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
We have defined a function, <code>popShift</code>, which takes an array as an argument and returns a new array. Modify the function, using <code>pop()</code> and <code>shift()</code>, to remove the first and last elements of the argument array, and assign the removed elements to their corresponding variables, so that the returned array contains their values.
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: <code>popShift(["challenge", "is", "not", "complete"])</code> should return <code>["challenge", "complete"]</code>
|
|
testString: assert.deepEqual(popShift(['challenge', 'is', 'not', 'complete']), ["challenge", "complete"], '<code>popShift(["challenge", "is", "not", "complete"])</code> should return <code>["challenge", "complete"]</code>');
|
|
- text: The <code>popShift</code> function should utilize the <code>pop()</code> method
|
|
testString: assert.notStrictEqual(popShift.toString().search(/\.pop\(/), -1, 'The <code>popShift</code> function should utilize the <code>pop()</code> method');
|
|
- text: The <code>popShift</code> function should utilize the <code>shift()</code> method
|
|
testString: assert.notStrictEqual(popShift.toString().search(/\.shift\(/), -1, 'The <code>popShift</code> function should utilize the <code>shift()</code> method');
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='js-seed'>
|
|
|
|
```js
|
|
function popShift(arr) {
|
|
let popped; // change this line
|
|
let shifted; // change this line
|
|
return [shifted, popped];
|
|
}
|
|
|
|
// do not change code below this line
|
|
console.log(popShift(['challenge', 'is', 'not', 'complete']));
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
```js
|
|
function popShift(arr) {
|
|
let popped = arr.pop(); // change this line
|
|
let shifted = arr.shift(); // change this line
|
|
return [shifted, popped];
|
|
}
|
|
```
|
|
</section>
|