JavaScript: Timing/Benchmark JS Code

Simple timing of a function

To get the timing of a JavaScript function, you just get a time stamp. Like this:

// the function to test
function range(n) {
  const arr = Array(n);
  for (let idx = 0; idx <= n; idx++) {
    arr[idx] = idx;
  }
  return arr;
}

{
  // timing

  const test_repeat_count = 50;

  const start = new Date().getTime();

  for (let i = 0; i < test_repeat_count; ++i) {
    range(9999);
  }

  const end = new Date().getTime();

  // result
  console.log(end - start);
}

Benchmark JavaScript Code Using Deno Bench

a better way is to use deno's builtin bench API.

https://deno.land/manual/tools/benchmarker

First, you need to create a file. Let's say bench.js

// bench.js
// 2022-07-10, 2022-08-27
// comparing speed of n = n + 1 vs n++

const f1 = ((x) => {
  let n = 1;
  for (let i = 1; i < x; i++) n = n + 1;
  return n;
});

const f2 = ((x) => {
  let n = 1;
  for (let i = 1; i < x; i++) n++;
  return n;
});

console.log(f1(10) === 10);
console.log(f2(10) === 10);

Deno.bench("normal assign", () => {
  f1(10_000);
});
Deno.bench("plus plus", () => {
  f2(10_000);
});

In the script, call

Deno.bench( a_name_string, arrow_function_of_no_arg);

then, in terminal, run this:

deno --unstable bench bench.js

this means, n = n + 1 and n++ have the same speed.

Array Push vs Unshift, Speed Comparison

• Array Push vs Unshift, Speed Comparison