window.onresize handler with a debounced calling to avoid unnecessary re-paints

onResize.js

/**
 * onResize.js
 *
 * `window.onresize` handler with a debounced calling to avoid unnecessary re-paints.
 *
 * e.g.:
 *   onResize.add(function(){
 *     console.log('Executed on window resize! But debounced.')
 *   })
 * 
 * Matías Lescano | @mjlescano
 * Licensed under the MIT license
 */

;if( !window.onResize ) (function(w){
  function debounce (func, wait, immediate) {
    var timeout
    return function () {
      var context = this
      var args = arguments
      var later = function () {
        timeout = null
        if (!immediate) func.apply(context, args)
      }
      var callNow = immediate && !timeout
      clearTimeout(timeout)
      timeout = setTimeout(later, wait)
      if (callNow) func.apply(context, args)
    }
  }
  
  var cbs = []
  
  var execute = debounce(function _execute() {
    for (var i = 0, l = cbs.length; i < l; i++) cbs[i]()
  }, 300)
  
  if (w.addEventListener) {
    w.addEventListener('resize', execute)
  } else {
    w.attachEvent('onresize', execute)
  }
  
  w.onResize = {
    add: function(cb){
      cbs.push(cb)
      return w.onResize
    },
    remove: function(cb){
      for (var i = 0, l = cbs.length; i < l; i++) {
        if (cb === cbs[i]) {
          cbs.splice(i,1)
          break
        }
      }
      return w.onResize
    }
  }
})(window);