14 lines
434 B
Markdown
14 lines
434 B
Markdown
### sumBy
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Returns the sum of an array, after mapping each element to a value using the provided function.
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Use `Array.map()` to map each element to the value returned by `fn`, `Array.reduce()` to add each value to an accumulator, initialized with a value of `0`.
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```js
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const sumBy = (arr, fn) => arr.map(fn).reduce((acc, val) => acc + val, 0);
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```
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```js
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sumBy([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], o => o.n); // 20
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```
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