unicorn/prefer-at Pedantic
What it does
Prefer the Array#at() and String#at() methods for index access.
This rule also discourages using 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:
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:
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
To enable this rule using the config file or in the CLI, you can use:
{
"rules": {
"unicorn/prefer-at": "error"
}
}import { defineConfig } from "oxlint";
export default defineConfig({
rules: {
"unicorn/prefer-at": "error",
},
});oxlint --deny unicorn/prefer-atVersion
This rule was added in v1.20.0.