Javascript 插件统一的实现步骤

步骤：

     // 1. 定义立即调用的函数
 +function($){
     "use strict";      //使用严格模式ES5支持
      //后续步骤
      // 2. xx 插件类及原型方法的定义
      // 3. 在jQuery上定义xx插件，并重设插件构造器
      // 4. 防冲突处理
      // 5. 绑定触发事件
 }(window.jQuery)

代码例子(bootstrap的alert.js)：

 /* ========================================================================
  * Bootstrap: alert.js v3.2.0
  * http://getbootstrap.com/javascript/#alerts
  * ========================================================================
  * Copyright 2011-2014 Twitter, Inc.
  * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
  * ======================================================================== */
 
 +function ($) {
   'use strict';
 
   // ALERT CLASS DEFINITION
   // ======================
 
   var dismiss = '[data-dismiss="alert"]'
   var Alert   = function (el) {
     $(el).on('click', dismiss, this.close)
   }
 
   Alert.VERSION = '3.2.0'
 
   Alert.prototype.close = function (e) {
     var $this    = $(this)
     var selector = $this.attr('data-target')
 
     if (!selector) {
       selector = $this.attr('href')
       selector = selector && selector.replace(/.*(?=#[^\s]*$)/, '') // strip for ie7
     }
 
     var $parent = $(selector)
 
     if (e) e.preventDefault()
 
     if (!$parent.length) {
       $parent = $this.hasClass('alert') ? $this : $this.parent()
     }
 
     $parent.trigger(e = $.Event('close.bs.alert'))
 
     if (e.isDefaultPrevented()) return
 
     $parent.removeClass('in')
 
     function removeElement() {
       // detach from parent, fire event then clean up data
       $parent.detach().trigger('closed.bs.alert').remove()
     }
 
     $.support.transition && $parent.hasClass('fade') ?
       $parent
         .one('bsTransitionEnd', removeElement)
         .emulateTransitionEnd(150) :
       removeElement()
   }
 
   // ALERT PLUGIN DEFINITION
   // =======================
 
   function Plugin(option) {
     return this.each(function () {
       var $this = $(this)
       var data  = $this.data('bs.alert')
 
       if (!data) $this.data('bs.alert', (data = new Alert(this)))
       if (typeof option == 'string') data[option].call($this)
     })
   }
 
   var old = $.fn.alert
 
   $.fn.alert             = Plugin
   $.fn.alert.Constructor = Alert
 
   // ALERT NO CONFLICT
   // =================
 
   $.fn.alert.noConflict = function () {
     $.fn.alert = old
     return this
   }
 
   // ALERT DATA-API
   // ==============
 
   $(document).on('click.bs.alert.data-api', dismiss, Alert.prototype.close)
 
 }(jQuery);