72 lines
2.9 KiB
Markdown
72 lines
2.9 KiB
Markdown
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---
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id: 587d7b87367417b2b2512b41
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title: Declare a Read-Only Variable with the const Keyword
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challengeType: 1
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---
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## Description
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<section id='description'>
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<code>let</code> is not the only new way to declare variables. In ES6, you can also declare variables using the <code>const</code> keyword.
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<code>const</code> has all the awesome features that <code>let</code> has, with the added bonus that variables declared using <code>const</code> are read-only. They are a constant value, which means that once a variable is assigned with <code>const</code>, it cannot be reassigned.
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<blockquote>"use strict"<br>const FAV_PET = "Cats";<br>FAV_PET = "Dogs"; // returns error</blockquote>
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As you can see, trying to reassign a variable declared with <code>const</code> will throw an error. You should always name variables you don't want to reassign using the <code>const</code> keyword. This helps when you accidentally attempt to reassign a variable that is meant to stay constant. A common practice when naming constants is to use all uppercase letters, with words separated by an underscore.
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</section>
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## Instructions
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<section id='instructions'>
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Change the code so that all variables are declared using <code>let</code> or <code>const</code>. Use <code>let</code> when you want the variable to change, and <code>const</code> when you want the variable to remain constant. Also, rename variables declared with <code>const</code> to conform to common practices, meaning constants should be in all caps.
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</section>
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## Tests
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<section id='tests'>
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```yml
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- text: <code>var</code> does not exist in your code.
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testString: 'getUserInput => assert(!getUserInput("index").match(/var/g),"<code>var</code> does not exist in your code.");'
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- text: <code>SENTENCE</code> should be a constant variable declared with <code>const</code>.
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testString: 'getUserInput => assert(getUserInput("index").match(/(const SENTENCE)/g), "<code>SENTENCE</code> should be a constant variable declared with <code>const</code>.");'
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- text: <code>i</code> should be declared with <code>let</code>.
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testString: 'getUserInput => assert(getUserInput("index").match(/(let i)/g), "<code>i</code> should be declared with <code>let</code>.");'
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- text: <code>console.log</code> should be changed to print the <code>SENTENCE</code> variable.
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testString: 'getUserInput => assert(getUserInput("index").match(/console\.log\(\s*SENTENCE\s*\)\s*;?/g), "<code>console.log</code> should be adjusted to print the variable <code>SENTENCE</code>.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function printManyTimes(str) {
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"use strict";
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// change code below this line
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var sentence = str + " is cool!";
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for(var i = 0; i < str.length; i+=2) {
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console.log(sentence);
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}
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// change code above this line
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}
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printManyTimes("freeCodeCamp");
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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