---
url: /docs/guide/usage/linter/rules/unicorn/prefer-at.md
---

### What it does

Prefer the [`Array#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at) and
[`String#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at)
methods for index access.

This rule also discourages using [`String#charAt()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charAt).
It also checks `String#substring()` calls that extract a single character.

### Why is this bad?

The `.at()` method is more readable and consistent for accessing elements by index,
especially for negative indices which access elements from the end of the array or string.

### Examples

Examples of **incorrect** code for this rule:

```js
const foo = array[array.length - 1];
const foo = array.slice(-1)[0];
const foo = string.charAt(string.length - 1);
```

Examples of **correct** code for this rule:

```js
const foo = array.at(-1);
const foo = array.at(-5);
const foo = string.at(-1);
```

## Configuration

This rule accepts a configuration object with the following properties:

### checkAllIndexAccess

type: `boolean`

default: `false`

Check all index access, not just special patterns like `array.length - 1`.
When enabled, `array[0]`, `array[1]`, etc. will also be flagged.

### getLastElementFunctions

type: `string[]`

default: `[]`

List of function names to treat as "get last element" functions.
These functions will be checked for `.at(-1)` usage.

## How to use

## Version

This rule was added in v1.20.0.

## References