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Update group-by

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Shortened code. It now also follows the styleguide more precisely. Improved description.
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Angelos Chalaris
2017-12-14 10:45:09 +02:00
committed by GitHub
parent e8d9acae9a
commit 91f393207d
1 changed files with 5 additions and 7 deletions
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snippets/group-by
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@ -1,16 +1,14 @@
### Group by ### Group by
Passing an array of values, a function or a property name thats going to be run against each value in the array, Use `Array.map()` to map the values of an array to a function or property name.
returns an object where the keys are the mapped results and the values is an array of the original values that generated the same results. Use `Array.reduce()` to create an object, where the keys are produced from the mapped results.
```js ```js
const groupBy = (values, fn) => { const groupBy = (arr, func) =>
return (typeof fn === 'function' ? values.map(fn) : values.map((val) => val[fn])) (typeof func === 'function' ? arr.map(func) : arr.map(val => val[func]))
.reduce((acc, val, i) => { .reduce((acc, val, i) => {
acc[val] = acc[val] === undefined ? [values[i]] : acc[val].concat(values[i]); acc[val] = acc[val] === undefined ? [arr[i]] : acc[val].concat(arr[i]); return acc;
return acc;
}, {}); }, {});
}
// groupBy([6.1, 4.2, 6.3], Math.floor) -> {4: [4.2], 6: [6.1, 6.3]} // groupBy([6.1, 4.2, 6.3], Math.floor) -> {4: [4.2], 6: [6.1, 6.3]}
// groupBy(['one', 'two', 'three'], 'length') -> {3: ['one', 'two'], 5: ['three']} // groupBy(['one', 'two', 'three'], 'length') -> {3: ['one', 'two'], 5: ['three']}
``` ```