partialLeft

Creates a new function with arguments pre-filled on the left.

Syntax

partialLeft<Args extends any[], R, P extends Partial<Args>>(
  callback: (...args: Args) => R,
  ...partial: P
): (...args: DropFirst<Args> extends P ? [] : DropFirst<Args>) => R

Parameters

Name	Type	Description
callback	(...args: Args) => R	Original function to be partially applied.
...partial	P	Arguments to be pre-filled on the left.

Returns

Type	Description
(...args: DropFirst<Args> extends P ? [] : DropFirst<Args>) => R	New function with partial arguments applied.

Example

const sum = (a: number, b: number, c: number) => a + b + c;
const partialSum = partialLeft(sum, 1);
partialSum(2, 3); // 6

Notes

• Throws a TypeError if the callback is not a function.
• Useful for creating specialized functions from generic ones.

References

• MDN: Partial application