Array tools in TypeScript

arraytools.ts

export const range = (start: number, stop: number, step: number=1) => {
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from#Sequence_generator_(range)
  return Array.from({ length: (stop - start - 1) / step + 1}, (_, i) => start + (i * step));
}

export const all = (values: any[]) => {
  for (let value of values) {
    if (!value) {
      return false;
    }
  }
  return true;
}

export const zip = (... lists: [... any[]]): [... any[]] => {
  const length = lists[0].length;
  return range(0, length).map(i => lists.map(l => l[i]));
}

export const combinations = <T>(list: T[], length: number): T[][] => {
  const pairs: T[][] = [];
  const set = (pair: T[], index: number) => {
    if (pair.length == length) {
      pairs.push(pair);
      return;
    }
    for (let i = index; i < list.length; i++) {
      set([... pair, list[i]], i + 1);
    }
  }
  set([], 0);
  return pairs;
}

export const product = <T>(... list: T[][]): T[][] => {
  const pairs: T[][] = [];
  const set = (pair: T[], index: number) => {
    if (pair.length === list.length) {
      pairs.push(pair);
      return;
    }
    for (let i of list[index]) {
      set([... pair, i], index + 1);
    }
  }
  set([], 0);
  return pairs;
}