24 lines
679 B
Markdown
24 lines
679 B
Markdown
---
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title: Max array value based on function
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tags: math,array
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expertise: beginner
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cover: blog_images/digital-nomad-4.jpg
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firstSeen: 2018-01-11T12:25:54+02:00
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lastUpdated: 2020-10-21T21:54:53+03:00
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---
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Returns the maximum value of an array, after mapping each element to a value using the provided function.
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- Use `Array.prototype.map()` to map each element to the value returned by `fn`.
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- Use `Math.max()` to get the maximum value.
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```js
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const maxBy = (arr, fn) =>
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Math.max(...arr.map(typeof fn === 'function' ? fn : val => val[fn]));
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```
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```js
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maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], x => x.n); // 8
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maxBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 8
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```
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