防抖函数

debounce.js

function debounce(func, wait, immediate) {
  var timeout

  return function() {
    var context = this
    var args = arguments

    if(timeout) clearTimeout(timeout)

    if (immediate) {
      var callNow = !timeout
      timeout = setTimeout(function() {
        timeout = null
      }, wait)
      if (callNow) func.apply(context, args)
    } else {
      timeout = setTimeout(function() {
        func.apply(context, args)
      }, wait)
    }
  }
}