Javascript Tip #4 - Measure function execution time

js-tip4.js

/* Tweet: https://twitter.com/AnsonH_/status/1436669886055415816?s=20 */

function slowFunction() {
  for (let i = 0; i < 999999999; ++i) {
    // do something...
  }
}


/***** Browser example *****/

const t0 = window.performance.now();

slowFunction();

const t1 = window.performance.now();
const timeTaken = t1 - t0;

console.log(`It took ${timeTaken} ms`);  // eg. "It took 836.1103000640869 ms"




/***** Node.js example *****/

const { performance } = require("perf_hooks");

const t0 = performance.now();

slowFunction();

const t1 = performance.now();
const timeTaken = t1 - t0;

console.log(`It took ${timeTaken} ms`);  // eg. "It took 836.1103000640869 ms"

Further links:

• Stack Overflow question on how to measure execution time
• MDN documentation on performance.now()