measure-performance-plain.js

const myMethod = () => {
    const startTimeInMs = new Date().getTime();

    // Do some heavy computation
    // ..........
    // ////////////////////////////////////////

    const endTimeInMs = new Date().getTime();
    const durationInMs = endTimeInMs - startTimeInMs;

    console.log(`myMethod took ${durationInMs} ms`);
};