21 lines
550 B
Markdown
21 lines
550 B
Markdown
### indexOfAll
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Returns all indices of `val` in an array. If `val` never occurs, returns `[-1]`.
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Use `Array.forEach()` to loop over elements and `Array.push()` to store indices for matching elements.
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Return `[-1]` if `length` of the array of indices is `0`, otherwise return the array of indices.
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``` js
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const indexOfAll = (arr, val) => {
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const indices = [];
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arr.forEach((el, i) => el === val && indices.push(i))
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return indices.length ? indices : [-1];
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};
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```
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``` js
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indexOfAll([1,2,3,1,2,3],1); // [0,3]
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indexOfAll([1,2,3],4); // [-1]
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```
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