68 lines
1.7 KiB
Markdown
68 lines
1.7 KiB
Markdown
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---
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id: 587d7b8c367417b2b2512b58
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title: Create an Export Fallback with export default
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challengeType: 1
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forumTopicId: 301199
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---
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## Description
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<section id='description'>
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In the <code>export</code> lesson, you learned about the syntax referred to as a <dfn>named export</dfn>. This allowed you to make multiple functions and variables available for use in other files.
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There is another <code>export</code> syntax you need to know, known as <dfn>export default</dfn>. Usually you will use this syntax if only one value is being exported from a file. It is also used to create a fallback value for a file or module.
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Below are examples using <code>export default</code>:
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```js
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// named function
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export default function add(x, y) {
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return x + y;
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}
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// anonymous function
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export default function(x, y) {
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return x + y;
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}
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```
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Since <code>export default</code> is used to declare a fallback value for a module or file, you can only have one value be a default export in each module or file. Additionally, you cannot use <code>export default</code> with <code>var</code>, <code>let</code>, or <code>const</code>
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</section>
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## Instructions
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<section id='instructions'>
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The following function should be the fallback value for the module. Please add the necessary code to do so.
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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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tests:
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- text: Your code should use <code>export</code> fallback.
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testString: assert(code.match(/export\s+default\s+function(\s+subtract\s*|\s*)\(\s*x,\s*y\s*\)\s*{/g));
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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 subtract(x, y) {
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return x - y;
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}
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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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export default function subtract(x, y) {
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return x - y;
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}
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```
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</section>
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