Function map

modules/katamari/src/main/ts/ephox/katamari/api/Arr.ts:62–72

(xs: ArrayLike<T>, f: ArrayMorphism<T, U>)

};

export const map = <T = any, U = any>(xs: ArrayLike<T>, f: ArrayMorphism<T, U>): U[] => {
  // pre-allocating array size when it's guaranteed to be known
  // http://jsperf.com/push-allocated-vs-dynamic/22
  const len = xs.length;
  const r = new Array(len);
  for (let i = 0; i < len; i++) {
    const x = xs[i];
    r[i] = f(x, i);
  }
  return r;
};

// Unwound implementing other functions in terms of each.
// The code size is roughly the same, and it should allow for better optimisation.