Skip to main content

NonEmptyArray<T>

NonEmptyArray<T> = [T, ...T[]]

An array type that guarantees at least one element.

Useful for functions that require non-empty input, avoiding runtime checks.

Type Parameters​

T: T​

The type of array elements

Since​

2.0.0

Example​

function first`<T>`(arr: `NonEmptyArray<T>`): T {
  return arr[0]; // ✅ Safe, TypeScript knows arr[0] exists
}

first([1, 2, 3]); // ✅ OK
first([]); // ❌ Error: Source has 0 element(s) but target requires 1

const items: `NonEmptyArray<string>` = ["a", "b"];
items[0]; // Type is `string`, not `string | undefined`