ltrim-array

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

Installation

Requires Node.js 6.0.0 or above.

npm i ltrim-array

API

The module exports a single function.

Parameters

1. Bindable: arr (Array or Array-like): The array that might have starting 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 beginning.

Examples

By default, ltrimArray() removes undefined elements from the beginning of an array.

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

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

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

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

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

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

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

To do more advanced filtering, provide a callback. Each element at the beginning 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 beginning, stopping when it reaches the string:

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

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

ltrimArray([undefined]) // []

The module also supports the bind operator:

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

Related

• rtrim-array: Removes specified values from the end of an array.