atAccesses

Prefer using .at() for accessing elements at negative indices.

✅ This rule is included in the ts stylistic and stylisticStrict presets.

Accessing an element at the end of an array or string using array[array.length - 1] is less readable than using the .at() method with a negative index. The .at() method provides a cleaner syntax for accessing elements from the end of a sequence.

Examples

❌ Incorrect

const last = array[array.length - 1];

const secondLast = items[items.length - 2];

const lastChar = text[text.length - 1];

✅ Correct

const last = array.at(-1);

const secondLast = items.at(-2);

const lastChar = text.at(-1);

const first = array[0];

const element = array[dynamicIndex];

Options

This rule is not configurable.

When Not To Use It

If you need to support environments that do not have the .at() method (pre-ES2022), or if your project has a polyfill that only covers certain cases, you can disable this rule.

Further Reading

• MDN: Array.prototype.at()
• MDN: String.prototype.at()

Equivalents in Other Linters

• Biome: useAtIndex
• ESLint: unicorn/prefer-at