Debounce

debounce.js

// Returns a function, that, as long as it continues to be invoked, will not be triggered. 
// The function will be called after it stops being called for N milliseconds. 

function debounce (cb, wait) {
  var timeoutID
  return function () {
    clearTimeout(timeoutID)
    timeoutID = setTimeout(cb, wait)
  }
}

debounceWithImmediate.js

// If `immediate` is passed, trigger the function on the leading edge, instead of the trailing.

function debounce (cb, wait, immediate) {
  var timeoutID
  return function () {
    function later () {
      timeoutID = null
      if (!timeoutID) {
        cb()
      }
    }
    var callNow = immediate && !timeoutID
    clearTimeout(timeoutID)
    timeoutID = setTimeout(later, wait)
    if (callNow) {
      cb()
    }
  }
}