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dropRightWhile()

dropRightWhile<T>(array, predicate): T[]

Creates a slice of array excluding elements dropped from the end. Elements are dropped until predicate returns falsey.

Type Parameters​

T: T​

The type of elements in the array.

Parameters​

array: readonly T[]​

The source array to query.

predicate: (value, index, array) => boolean​

The function invoked per iteration.

Returns: T[]​

A new array with the trailing elements dropped.

Since​

2.0.0

Performance​

O(n) time & space. Uses for loop with early return (break) for optimal performance when dropping few elements.

Also known as​

dropLastWhile (Remeda, Ramda) · dropRightWhile (Lodash, es-toolkit, Modern Dash) · ❌ (Radashi, Effect, Antfu)

Example​

dropRightWhile([1, 2, 3, 4, 5], (v) => v > 2);
// => [1, 2]

dropRightWhile(
  [{ name: 'Alice', active: true }, { name: 'Bob', active: false }],
  (u) => !u.active
);
// => [{ name: 'Alice', active: true }]

How it works?​

Drops elements from the end while the predicate returns true. Scans from right to left.

Use Cases​

Trim trailing empty or whitespace strings 📌​

Remove trailing empty or invalid entries from an array. Perfect for cleaning up user inputs, CSV parsing, or form data with trailing blanks.

const inputs = ["Alice", "Bob", "Charlie", "", "", ""];

const cleanedInputs = dropRightWhile(inputs, (val) => val === "");
// => ["Alice", "Bob", "Charlie"]

Remove trailing zeros or placeholder values​

Drop trailing numeric placeholders or padding from data arrays. Perfect for trimming sensor data, audio buffers, or fixed-length records.

const audioSamples = [0.5, 0.8, 0.3, 0.1, 0, 0, 0];

const trimmedSamples = dropRightWhile(audioSamples, (val) => val === 0);
// => [0.5, 0.8, 0.3, 0.1]

Exclude recent/future entries from sorted data​

Drop trailing elements from a sorted array based on a date or value threshold. Perfect for excluding future-dated records, pending transactions, or draft entries.

const posts = [
  { title: "Post 1", status: "published" },
  { title: "Post 2", status: "published" },
  { title: "Post 3", status: "draft" },
  { title: "Post 4", status: "draft" },
];

const publishedPosts = dropRightWhile(posts, (p) => p.status === "draft");
// => [{ title: "Post 1", status: "published" }, { title: "Post 2", status: "published" }]