Partial function with placeholders

90.0% acceptance

Mar 31, 2026

Given a function fn and an array args, return a function partialFn. Placeholders "_" in the args should be replaced with values from restArgs starting from index 0. Any remaining values in the restArgs should be added at the end of the args. partialFn should return a result of fn. fn should be called with the elements of the modified args passed as separate arguments.

Solution

TypeScript

Time O(n)

Space O(1)

LeetCode

solution.ts

type JSONValue =
  | null
  | boolean
  | number
  | string
  | JSONValue[]
  | { [key: string]: JSONValue };
type Fn = (...args: JSONValue[]) => JSONValue;

function partial(fn: Fn, args: JSONValue[]): Fn {
  return function (...restArgs) {
  const result: JSONValue[] = [];
  let restIdx = 0;
  for (const arg of args) {
    if (arg === "_") {
    result.push(restArgs[restIdx++]);
    } else {
    result.push(arg);
    }
  }
  while (restIdx < restArgs.length) {
    result.push(restArgs[restIdx++]);
  }
  return fn(...result);
  };
}