Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Improve Array.p.shift() algorithm description #38171

Merged
merged 1 commit into from
Feb 16, 2025
+2 −4
Merged

Improve Array.p.shift() algorithm description #38171

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 2 additions & 4 deletions files/en-us/web/javascript/reference/global_objects/array/shift/index.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -41,9 +41,7 @@ The removed element from the array; {{jsxref("undefined")}} if the array is empt

## Description

The `shift()` method removes the element at the zeroth index and shifts the
values at consecutive indexes down, then returns the removed value. If the
{{jsxref("Array/length", "length")}} property is 0, {{jsxref("undefined")}} is returned.
The `shift()` method shifts all values to the left by 1 and decrements the length by 1, resulting in the first element being removed. If the {{jsxref("Array/length", "length")}} property is 0, {{jsxref("undefined")}} is returned.

The {{jsxref("Array/pop", "pop()")}} method has similar behavior to `shift()`, but applied to the last element in an array.

Expand Down Expand Up @@ -89,7 +87,7 @@ while (typeof (i = names.shift()) !== "undefined") {

### Calling shift() on non-array objects

The `shift()` method reads the `length` property of `this`. If the [normalized length](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#normalization_of_the_length_property) is 0, `length` is set to `0` again (whereas it may be negative or `undefined` before). Otherwise, the property at `0` is returned, and the rest of the properties are shifted left by one. The `length` property is decremented by one.
The `shift()` method reads the `length` property of `this`. If the [normalized length](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#normalization_of_the_length_property) is 0, `length` is set to `0` again (whereas it may be negative or `undefined` before). Otherwise, the property at `0` is returned, and the rest of the properties are shifted left by one. The property at `length - 1` is [deleted](/en-US/docs/Web/JavaScript/Reference/Operators/delete), and the `length` property is decremented by one.

```js
const arrayLike = {
Expand Down