how to measure function performance in javascript

how to measure function performance in javascript

Performance API

1. Performance Timeline API
2. Navigation Timing API
3. User Timing API
4. 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();

refs

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

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

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

https://www.sitepoint.com/measuring-javascript-functions-performance/

https://levelup.gitconnected.com/different-ways-to-measure-performance-in-javascript-94785075ab96

https://stackoverflow.com/questions/313893/how-to-measure-time-taken-by-a-function-to-execute

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