Remove array elements from the end until condition is met
JavaScript, Array · Nov 29, 2020

Removes elements from the end of an array until the passed function returns true
.
Returns the removed elements.
- Create a reversed copy of the array, using the spread operator (
...
) andArray.prototype.reverse()
. - Loop through the reversed copy, using a
for...of
loop overArray.prototype.entries()
until the returned value from the function is truthy. - Return the removed elements, using
Array.prototype.slice()
. - The callback function,
fn
, accepts a single argument which is the value of the element.
const takeRightUntil = (arr, fn) => {
for (const [i, val] of [...arr].reverse().entries())
if (fn(val)) return i === 0 ? [] : arr.slice(-i);
return arr;
};
takeRightUntil([1, 2, 3, 4], n => n < 3); // [3, 4]