unicorn/no-array-reverse

reverse() reverses the array in place and returns that same array. After const newestFirst = posts.reverse(), posts is reversed too. toReversed() returns a new array and leaves the original alone.

--fix-suggestions replaces reverse with toReversed.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"unicorn/no-array-reverse" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"unicorn/no-array-reverse" = ["error", {
  allowExpressionStatement = true,
}]

Examples#

example.js1 problem

const newestFirst = posts.reverse();

Copying the array first is reported too, because toReversed() already makes a copy:

example.js1 problem

const newestFirst = [...posts].reverse();

example.jsNo problems

const newestFirst = posts.toReversed();

A call used as a standalone statement is allowed by default. Nothing uses the result, so changing the array is the point:

example.jsNo problems

posts.reverse();

Options#

Option	Default	What it does
`allowExpressionStatement`	`true`	Allow `array.reverse();` as a standalone statement.

example.jswith { "allowExpressionStatement": false }1 problem

posts.reverse();

When not to use it#

toReversed() is part of ES2023. Turn the rule off if your code needs to run somewhere that doesn't have it.