23 lines
643 B
Markdown
23 lines
643 B
Markdown
---
|
|
title: takeWhile
|
|
tags: array,intermediate
|
|
---
|
|
|
|
Removes elements in an array until the passed function returns `false`.
|
|
Returns the removed elements.
|
|
|
|
- Loop through the array, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is falsy.
|
|
- Return the removed elements, using `Array.prototype.slice()`.
|
|
- The callback function, `fn`, accepts a single argument which is the value of the element.
|
|
|
|
```js
|
|
const takeWhile = (arr, fn) => {
|
|
for (const [i, val] of arr.entries()) if (!fn(val)) return arr.slice(0, i);
|
|
return arr;
|
|
};
|
|
```
|
|
|
|
```js
|
|
takeWhile([1, 2, 3, 4], n => n < 3); // [1, 2]
|
|
```
|