29 lines
942 B
Markdown
29 lines
942 B
Markdown
---
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title: Remove array elements from the end until condition is met
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type: snippet
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language: javascript
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tags: [array]
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cover: fruit-feast
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dateModified: 2020-11-29T12:04:53+02:00
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---
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Removes elements from the end of an array until the passed function returns `true`.
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Returns the removed elements.
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- Create a reversed copy of the array, using the spread operator (`...`) and `Array.prototype.reverse()`.
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- Loop through the reversed copy, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is truthy.
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- Return the removed elements, using `Array.prototype.slice()`.
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- The callback function, `fn`, accepts a single argument which is the value of the element.
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```js
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const takeRightUntil = (arr, fn) => {
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for (const [i, val] of [...arr].reverse().entries())
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if (fn(val)) return i === 0 ? [] : arr.slice(-i);
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return arr;
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};
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```
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```js
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takeRightUntil([1, 2, 3, 4], n => n < 3); // [3, 4]
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```
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