prefer-negative-index
March 27, 2026 · View on GitHub
📝 Prefer negative index over .length - index when possible.
💼 This rule is enabled in the following configs: ✅ recommended, ☑️ unopinionated.
🔧 This rule is automatically fixable by the --fix CLI option.
Prefer negative index over calculating from .length for:
String#slice()Array#slice()TypedArray#slice()String#at()Array#at()TypedArray#at()Array#splice()Array#toSpliced()Array#with()TypedArray#with()TypedArray#subarray()
Examples
// ❌
foo.slice(foo.length - 2, foo.length - 1);
// ✅
foo.slice(-2, -1);
// ❌
foo.splice(foo.length - 1, 1);
// ✅
foo.splice(-1, 1);
// ❌
foo.at(foo.length - 1);
// ✅
foo.at(-1);
// ❌
Array.prototype.slice.call(foo, foo.length - 2, foo.length - 1);
// ✅
Array.prototype.slice.call(foo, -2, -1);
// ❌
Array.prototype.slice.apply(foo, [foo.length - 2, foo.length - 1]);
// ✅
Array.prototype.slice.apply(foo, [-2, -1]);