29 lines
986 B
Markdown
29 lines
986 B
Markdown
---
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title: Remove list elements from the end while condition is met
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tags: array
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expertise: intermediate
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cover: blog_images/beach-pineapple.jpg
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firstSeen: 2018-01-26T12:55:31+02:00
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lastUpdated: 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 `false`.
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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 falsy.
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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 takeRightWhile = (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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takeRightWhile([1, 2, 3, 4], n => n >= 3); // [3, 4]
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```
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