Plain JavaScript implementations of common jQuery functions

BrowserSupport

List of the browsers which support the features:

- IE9+
- Firefox 3.5+
- Opera 9+
- Safari 4+
- Chrome 1+
- iPhone and iPad iOS1+
- Android phone and tablets 2.1+
- Blackberry OS6+
- Windows 7.5+
- Mobile Firefox
- Opera Mobile

If you only need to support more modern browsers like IE10+, Chrome, Firefox, Opera and Safari, you could also start using the HTML5 classList functionality, which makes adding and removing classes easy.

hasClass

// Takes two params: element and classname
function hasClass(el, cls) {
  return el.className && new RegExp("(\\s|^)" + cls + "(\\s|$)").test(el.className);
}

HTML5Classlist

/** 
 * If you only need to support more modern browsers like IE10+, 
 * Chrome, Firefox, Opera and Safari, you could also start using 
 * HTML5’s classList functionality which makes adding and removing 
 * classes even easier.
 */

if ("classList" in document.documentElement) {
  // Add class
  element.classList.add("bar");
  
  // Remove class
  element.classList.remove("foo");
  
  // Check if element has class
  element.classList.contains("foo");
  
  // Toggle class
  element.classList.toggle("active");
}

removeClass

// Takes two params: element and classname
function removeClass(el, cls) {
  var reg = new RegExp("(\\s|^)" + cls + "(\\s|$)");
  el.className = el.className.replace(reg, " ").replace(/(^\s*)|(\s*$)/g,"");
}