how to measure function performance in javascript

Performance API

Performance Timeline API
Navigation Timing API
User Timing API
Resource Timing API.

https://developer.mozilla.org/en-US/docs/Web/API/Performance

performance.measure

performance.measure(name);

performance.measure(name, startMark);

performance.measure(name, startMark, endMark);

performance.measure(name, undefined, endMark);

performance.mark

performance.mark(name);

performance.now

const t1 = performance.now();

// do somethings

const t2 = performance.now();

High Resolution Time Level 2

W3C Recommendation 21 November 2019

https://www.w3.org/TR/hr-time/



const log = console.log;

const noForArrayAutoGenerator = (len = 100) => {

  return [...``.padStart(len, ` `)].map((item, i) => i + 1).map((item, i) => i % 2 === 0 ? item : item + ``);

}

const arr = noForArrayAutoGenerator(1000 * 100);

function test(arr = []) {

  const begin = performance.now();

  for (let i = 0; i < arr.length; i++) {

    // log(`item${i}`, arr[i]);

  }

  const end = performance.now();

  const result = end - begin;

  log(`result`, result)

}

test();

console.time & console.timeEnd

无返回值️



const log = console.log;

console.time(`label`);

setTimeout(() => log(`zero`), 1000);

// 62

console.timeEnd(`label`);

// label: 16111.451171875 ms

https://developer.mozilla.org/en-US/docs/Web/API/Console/timeEnd

https://developer.mozilla.org/en-US/docs/Web/API/Console/time

console.log & new Date().getTime()



// new Date().getTime()

demos

"use strict";

/**

 *

 * @author xgqfrms

 * @license MIT

 * @copyright xgqfrms

 * @created 2020-07-20

 * @modified

 *

 * @description performance

 * @difficulty Easy Medium Hard

 * @complexity O(n)

 * @augments

 * @example

 * @link

 * @solutions

 *

 */

const log = console.log;

const noForArrayAutoGenerator = (len = 100) => {

  return [...``.padStart(len, ` `)].map((item, i) => i + 1).map((item, i) => i % 2 === 0 ? item : item + ``);

}

// const arr = noForArrayAutoGenerator(1);

// const arr = noForArrayAutoGenerator(100);

const arr = noForArrayAutoGenerator(10000);

// const arr = noForArrayAutoGenerator(10000 * 10);

// const arr = noForArrayAutoGenerator(10000 * 1000);

function test(arr = []) {

  // ReferenceError: performance is not defined

  const begin = performance.now();

  for (let i = 0; i < arr.length; i++) {

    // log(`item${i}`, arr[i]);

  }

  const end = performance.now();

  const result = end - begin;

  log(`result`, result)

}

test();