concat-vs-spread-operator.js

const a = Array(100000).fill(Math.random());
const b = Array(100000).fill(Math.random());

const benchmark = (func, repeat) => {
  const result = [];
  Array(repeat)
    .fill(1)
    .map(() => {
      const start = window.performance.now();
      func();
      const end = window.performance.now();
      const time = end - start;
      result.push(time);
    });
  const average = result.reduce((total, t) => total + t) / repeat;
  console.table({ try: repeat, average });
};

benchmark(() => [...a, ...b], 1000);
benchmark(() => a.concat(b), 1000);