1.1.0 • Public • Published


Removes specified values from the end of an array. Analogous to a right-trim operation for strings, except this module tests array elements instead of string characters.


Requires Node.js 6.0.0 or above.

npm i rtrim-array


The module exports a single function.


  1. Bindable: arr (Array or Array-like): The array that might have ending elements to be removed.
  2. Optional: trim (any): A Function that tests elements (returning true if the element should be trimmed), or an Array of elements to be trimmed, or any single value that should be trimmed. If this argument is omitted, then undefined will be trimmed.

Return Value

A copy of arr, with any trimmable elements removed from the end.


By default, rtrimArray() removes undefined elements from the end of an array.

const rtrimArray = require('rtrim-array')
rtrimArray([1, 2, 3, undefined, undefined]) // [1, 2, 3]

This operation is distinct from that of Array.prototype.filter() because rtrimArray() only removes from the end. If a trimmable value (in this case, undefined) is found at the beginning or in the middle of the array, it will not be removed:

rtrimArray([1, undefined, 3, undefined, undefined]) // [1, undefined, 3]

If you want to trim something besides undefined, provide it as the second argument:

rtrimArray([1, 2, 3, undefined, null], null) // [1, 2, 3, undefined]

If you want more than one value to be trimmed, put the values in an array and provide it as the second argument:

rtrimArray([1, 2, 3, null, false, null], [false, null]) // [1, 2, 3]

To do more advanced filtering, provide a callback. Each element on the end will be passed to the callback, and if the callback returns true, the element will be trimmed. If the callback returns false, the trimming will stop. In this example, the callback causes the module to trim numbers from the end, stopping when it reaches the string:

rtrimArray([1, '2', 3, 4, 5], el => typeof el === 'number') // [1, '2']

If every element in the array is trimmable, an empty array will be returned:

rtrimArray([undefined]) // []

The module also supports the bind operator:

const rtrim = require('rtrim-array')
[1, 2, 3, undefined, undefined]::rtrim() // [1, 2, 3]
[1, 2, 3, undefined, null]::rtrim(null)  // [1, 2, 3, undefined]


  • ltrim-array: Removes specified values from the beginning of an array.

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