最近写了一个红包雨的小功能，但感觉自己的js还有很多地方可以提高，望大神们可以帮忙指点一二

 1 ‘use strict‘;
 2 function RedEnvelope(options){
 3     if(this === window){
 4         return new RedEnvelope(options);
 5     }
 6     var defaults = {
 7         imgWidth:60,//红包的宽度
 8         position:‘absolute‘,
 9         imgEnvSrc:‘../images/game/redEnv/redEnv.png‘,
10         containerClass:‘.redEnv-contain‘
11     };
12     if(!options){
13         options = defaults;
14     }else{
15         for (var option in defaults) {
16             if (typeof options[option] === undefined) {
17                 options[option] = defaults[option];
18             }
19         }
20     }
21     this.options = options;
22     this.createEnv();
23 }
24 RedEnvelope.prototype.createEnv = function(){
25     var imgEnv = document.createElement(‘img‘);
26     imgEnv.src = this.options.imgEnvSrc;
27     imgEnv.style.width = this.options.imgWidth+‘px‘;
28     this.evnPosition(imgEnv);
29 }
30 RedEnvelope.prototype.evnPosition = function(img){
31     var containerWidth = $(this.options.containerClass).width();
32     var containerHeight = window.screen.height;
33     $(this.options.containerClass).prepend(img);
34     //红包初始的位置
35     img.style.position = this.options.position;
36     var startTop = parseInt(Math.random()*10+(-10))
37     var startLeft = parseInt(Math.random()*containerWidth);
38     //移动的位置
39     var moveLeft = parseInt(Math.random()*containerWidth+(-30));
40     var t=parseInt(Math.random() * 1000+1200);
41     this.evnAnimation({‘startLeft‘:startLeft, ‘startTop‘:startTop, ‘moveLeft‘:moveLeft,‘moveTop‘:containerHeight},t);
42 }
43 /*添加元素到主内容上*/
44 RedEnvelope.prototype.evnAnimation =  function (posObject,time){
45     $(this.options.containerClass).children(‘img:first‘).css({‘left‘:posObject.startLeft,‘top‘:posObject.startTop});
46     $(this.options.containerClass).children(‘img:first‘).animate(
47         {
48             ‘left‘:posObject.startLeft-posObject.moveLeft,
49             ‘top‘:posObject.moveTop
50         },
51         time,
52         ‘linear‘,
53         function(){
54             $(this).remove();
55         }
56     );
57