24 Modern ES6 Code Snippets to Solve Practical JavaScript Problems

This article, originally published on the "前端之巅" public account, compiles 24 useful ES6 code snippets that solve a variety of practical JavaScript problems encountered in front‑end development.

1. How to hide all specified elements?

const hide = (...el) => [...el].forEach(e => (e.style.display = 'none'));
// Example
hide(document.querySelectorAll('img')); // hides all
elements

2. How to check if an element has a specific class?

const hasClass = (el, className) => el.classList.contains(className);
// Example
hasClass(document.querySelector('p.special'), 'special'); // true

3. How to toggle a class on an element?

const toggleClass = (el, className) => el.classList.toggle(className);
// Example
toggleClass(document.querySelector('p.special'), 'special'); // class removed

4. How to get the current scroll position of the page?

const getScrollPosition = (el = window) => ({
  x: el.pageXOffset !== undefined ? el.pageXOffset : el.scrollLeft,
  y: el.pageYOffset !== undefined ? el.pageYOffset : el.scrollTop
});
// Example
getScrollPosition(); // {x: 0, y: 200}

5. How to smoothly scroll to the top of the page?

const scrollToTop = () => {
  const c = document.documentElement.scrollTop || document.body.scrollTop;
  if (c > 0) {
    window.requestAnimationFrame(scrollToTop);
    window.scrollTo(0, c - c / 8);
  }
};
// Example
scrollToTop();

6. How to determine whether a parent element contains a child element?

const elementContains = (parent, child) => parent !== child && parent.contains(child);
// Examples
elementContains(document.querySelector('head'), document.querySelector('title')); // true
elementContains(document.querySelector('body'), document.querySelector('body')); // false

7. How to check if an element is visible in the viewport?

const elementIsVisibleInViewport = (el, partiallyVisible = false) => {
  const { top, left, bottom, right } = el.getBoundingClientRect();
  const { innerHeight, innerWidth } = window;
  return partiallyVisible
    ? ((top > 0 && top < innerHeight) || (bottom > 0 && bottom < innerHeight)) &&
      ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth))
    : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth;
};
// Examples
elementIsVisibleInViewport(el); // not fully visible
elementIsVisibleInViewport(el, true); // partially visible

8. How to get all images inside an element?

const getImages = (el, includeDuplicates = false) => {
  const images = [...el.getElementsByTagName('img')].map(img => img.getAttribute('src'));
  return includeDuplicates ? images : [...new Set(images)];
};
// Examples
getImages(document, true); // all images including duplicates
getImages(document, false); // unique image sources

9. How to detect whether the device is mobile or desktop?

const detectDeviceType = () =>
  /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)
    ? 'Mobile'
    : 'Desktop';
// Example
detectDeviceType(); // "Mobile" or "Desktop"

10. How to get the current URL?

const currentURL = () => window.location.href;
// Example
currentURL(); // "https://example.com"

11. How to create an object from URL query parameters?

const getURLParameters = url =>
  (url.match(/([^?=&]+)(=([^&]*))/g) || []).reduce(
    (a, v) => ((a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1)), a),
    {}
  );
// Examples
getURLParameters('http://url.com/page?n=Adam&s=Smith'); // {n: 'Adam', s: 'Smith'}
getURLParameters('google.com'); // {}

12. How to encode a group of form elements into an object?

const formToObject = form =>
  Array.from(new FormData(form)).reduce(
    (acc, [key, value]) => ({ ...acc, [key]: value }),
    {}
  );
// Example
formToObject(document.querySelector('#form')); // { email: '[email protected]', name: 'Test Name' }

13. How to retrieve a set of properties from an object using a selector string?

const get = (from, ...selectors) =>
  [...selectors].map(s =>
    s
      .replace(/\[([^\[\]]*)\]/g, '.$1')
      .split('.')
      .filter(t => t !== '')
      .reduce((prev, cur) => prev && prev[cur], from)
  );
// Example
const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] };
get(obj, 'selector.to.val', 'target[0]', 'target[2].a'); // ['val to select', 1, 'test']

14. How to delay execution of a function by a given number of milliseconds?

const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
// Example
delay(function(text) { console.log(text); }, 1000, 'later'); // logs "later" after 1 second

15. How to trigger a specific event on an element with optional custom data?

const triggerEvent = (el, eventType, detail) =>
  el.dispatchEvent(new CustomEvent(eventType, { detail }));
// Examples
triggerEvent(document.getElementById('myId'), 'click');
triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });

16. How to remove an event listener from an element?

const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);
const fn = () => console.log('!');
document.body.addEventListener('click', fn);
off(document.body, 'click', fn); // listener removed

17. How to format a duration given in milliseconds into a readable string?

const formatDuration = ms => {
  if (ms < 0) ms = -ms;
  const time = {
    day: Math.floor(ms / 86400000),
    hour: Math.floor(ms / 3600000) % 24,
    minute: Math.floor(ms / 60000) % 60,
    second: Math.floor(ms / 1000) % 60,
    millisecond: Math.floor(ms) % 1000
  };
  return Object.entries(time)
    .filter(val => val[1] !== 0)
    .map(([key, val]) => `${val} ${key}${val !== 1 ? 's' : ''}`)
    .join(', ');
};
// Examples
formatDuration(1001); // "1 second, 1 millisecond"
formatDuration(34325055574); // "397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds"

18. How to calculate the number of days between two dates?

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
  (dateFinal - dateInitial) / (1000 * 3600 * 24);
// Example
getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9

19. How to perform a GET request to a given URL?

const httpGet = (url, callback, err = console.error) => {
  const request = new XMLHttpRequest();
  request.open('GET', url, true);
  request.onload = () => callback(request.responseText);
  request.onerror = () => err(request);
  request.send();
};
// Example
httpGet('https://jsonplaceholder.typicode.com/posts/1', console.log);

20. How to perform a POST request to a given URL?

const httpPost = (url, data, callback, err = console.error) => {
  const request = new XMLHttpRequest();
  request.open('POST', url, true);
  request.setRequestHeader('Content-type', 'application/json; charset=utf-8');
  request.onload = () => callback(request.responseText);
  request.onerror = () => err(request);
  request.send(data);
};
const newPost = { userId: 1, id: 1337, title: 'Foo', body: 'bar bar bar' };
const data = JSON.stringify(newPost);
httpPost('https://jsonplaceholder.typicode.com/posts', data, console.log);
// Logs created post

21. How to create a timer for a selector with a range, step, and duration?

const counter = (selector, start, end, step = 1, duration = 2000) => {
  let current = start,
    _step = (end - start) * step < 0 ? -step : step,
    timer = setInterval(() => {
      current += _step;
      document.querySelector(selector).innerHTML = current;
      if (current >= end) document.querySelector(selector).innerHTML = end;
      if (current >= end) clearInterval(timer);
    }, Math.abs(Math.floor(duration / (end - start))));
  return timer;
};
// Example
counter('#my-id', 1, 1000, 5, 2000); // 2‑second counter

22. How to copy a string to the clipboard?

const copyToClipboard = str => {
  const el = document.createElement('textarea');
  el.value = str;
  el.setAttribute('readonly', '');
  el.style.position = 'absolute';
  el.style.left = '-9999px';
  const selected = document.getSelection().rangeCount > 0 ? document.getSelection().getRangeAt(0) : false;
  el.select();
  document.execCommand('copy');
  document.body.removeChild(el);
  if (selected) {
    document.getSelection().removeAllRanges();
    document.getSelection().addRange(selected);
  }
};
// Example
copyToClipboard('Lorem ipsum'); // copies text

23. How to determine if the browser tab is currently focused?

const isBrowserTabFocused = () => !document.hidden;
// Example
isBrowserTabFocused(); // true

24. How to create a directory if it does not exist?

const fs = require('fs');
const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);
// Example
createDirIfNotExists('test'); // creates "test" directory if missing

These snippets provide quick, reusable solutions for everyday JavaScript tasks, helping developers write cleaner and more efficient code.