Basic performance tests of the spread operator

spreadTest.js

const numberFormat = new Intl.NumberFormat("en-US", { style: "decimal" });

const TEST_ARRAY_SIZE = 1000;
const TEST_COUNT = 1000;

const pushUsingPush = (arr) => {
  arr.push(5);
  return arr;
};

const pushUsingSpread = (arr) => {
  return [...arr, 5];
};

const unshiftUsingUnshift = (arr) => {
  arr.unshift(5);
  return arr;
};

const unshiftUsingSpread = (arr) => {
  return [5, ...arr];
};

const copyUsingSpread = (arr) => {
  return [...arr];
};

const copyUsingStructuredClone = (arr) => {
  return structuredClone(arr);
};

const testOperation = (fn, title) => {
  // Create the test arrays
  const arrays = new Array(TEST_COUNT)
    .fill(0)
    .map(() => new Array(TEST_ARRAY_SIZE).fill(0).map(() => Math.random()));

  // Run the function against every test array
  const start = performance.now();
  for (const arr of arrays) {
    fn(arr);
  }
  const end = performance.now();

  console.log(
    `${title
      .padEnd(27)
      .replace("{count}", numberFormat.format(TEST_ARRAY_SIZE))}: ${(
      (end - start) /
      TEST_COUNT
    ).toFixed(3)} ms/op`
  );
};

testOperation(copyUsingStructuredClone, `copy {count} / clone`);
testOperation(copyUsingSpread, `copy {count} / spread`);

testOperation(pushUsingPush, `push onto {count} / push`);
testOperation(pushUsingSpread, `push onto {count} / spread`);

testOperation(unshiftUsingUnshift, `unshift {count} / unshift`);
testOperation(unshiftUsingSpread, `unshift {count} / spread`);