84 lines
2.5 KiB
Markdown
84 lines
2.5 KiB
Markdown
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---
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id: a97fd23d9b809dac9921074f
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title: Arguments Optional
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isRequired: true
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challengeType: 5
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guideUrl: 'https://guide.freecodecamp.org/certificates/arguments-optional'
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---
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## Description
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<section id='description'>
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Create a function that sums two arguments together. If only one argument is provided, then return a function that expects one argument and returns the sum.
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For example, <code>addTogether(2, 3)</code> should return <code>5</code>, and <code>addTogether(2)</code> should return a function.
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Calling this returned function with a single argument will then return the sum:
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<code>var sumTwoAnd = addTogether(2);</code>
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<code>sumTwoAnd(3)</code> returns <code>5</code>.
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If either argument isn't a valid number, return undefined.
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Remember to use <a href='http://forum.freecodecamp.org/t/how-to-get-help-when-you-are-stuck/19514' target='_blank'>Read-Search-Ask</a> if you get stuck. Try to pair program. Write your own code.
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</section>
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## Instructions
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<section id='instructions'>
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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>addTogether(2, 3)</code> should return 5.'
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testString: 'assert.deepEqual(addTogether(2, 3), 5, "<code>addTogether(2, 3)</code> should return 5.");'
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- text: <code>addTogether(2)(3)</code> should return 5.
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testString: 'assert.deepEqual(addTogether(2)(3), 5, "<code>addTogether(2)(3)</code> should return 5.");'
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- text: '<code>addTogether("http://bit.ly/IqT6zt")</code> should return undefined.'
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testString: 'assert.isUndefined(addTogether("http://bit.ly/IqT6zt"), "<code>addTogether("http://bit.ly/IqT6zt")</code> should return undefined.");'
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- text: '<code>addTogether(2, "3")</code> should return undefined.'
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testString: 'assert.isUndefined(addTogether(2, "3"), "<code>addTogether(2, "3")</code> should return undefined.");'
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- text: '<code>addTogether(2)([3])</code> should return undefined.'
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testString: 'assert.isUndefined(addTogether(2)([3]), "<code>addTogether(2)([3])</code> should return undefined.");'
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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 addTogether() {
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return false;
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}
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addTogether(2,3);
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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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function addTogether() {
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var a = arguments[0];
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if (toString.call(a) !== '[object Number]') return;
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if (arguments.length === 1) {
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return function(b) {
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if (toString.call(b) !== '[object Number]') return;
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return a + b;
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};
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}
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var b = arguments[1];
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if (toString.call(b) !== '[object Number]') return;
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return a + arguments[1];
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}
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```
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</section>
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