Bench.js

function memoize(fn) {
  return function() {
    var args = Array.prototype.slice.call(arguments);
    fn.cache = fn.cache || {};
    return fn.cache[args]
      ? fn.cache[args]
      : (fn.cache[args] = fn.apply(this, args));
  };
}

function sqrt(arg) {
  return Math.sqrt(arg);
}

const memoizedSqrt = memoize(sqrt);

console.time('Do nothing');
// do nothing
console.timeEnd('Do nothing'); // 0.064ms

console.time('memoized call');
memoizedSqrt(4);
console.timeEnd('memoized call'); // 0.157ms

console.time('non-memoized call');
memoizedSqrt(4);
console.timeEnd('non-memoized call'); // 0.015ms

console.time('Direct, no caching');
sqrt(4);
console.timeEnd('Direct, no caching'); // 0.003ms - I guess this is mostly `console.time`

console.time('Direct, no caching');
sqrt(4);
console.timeEnd('Direct, no caching'); // 0.002ms

console.time('Direct, no caching');
sqrt(4);
console.timeEnd('Direct, no caching'); // 0.001ms

console.time('Do nothing');
// do nothing
console.timeEnd('Do nothing'); // 0.001ms - compare this with the first 'Do nothing'