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

js部分

 'use strict';
 function RedEnvelope(options){
     if(this === window){
         return new RedEnvelope(options);
     }
     var defaults = {
         imgWidth:60,//红包的宽度
         position:'absolute',
         imgEnvSrc:'../images/game/redEnv/redEnv.png',
         containerClass:'.redEnv-contain'
     };
     if(!options){
         options = defaults;
     }else{
         for (var option in defaults) {
             if (typeof options[option] === undefined) {
                 options[option] = defaults[option];
             }
         }
     }
     this.options = options;
     this.createEnv();
 }
 RedEnvelope.prototype.createEnv = function(){
     var imgEnv = document.createElement('img');
     imgEnv.src = this.options.imgEnvSrc;
     imgEnv.style.width = this.options.imgWidth+'px';
     this.evnPosition(imgEnv);
 }
 RedEnvelope.prototype.evnPosition = function(img){
     var containerWidth = $(this.options.containerClass).width();
     var containerHeight = window.screen.height;
     $(this.options.containerClass).prepend(img);
     //红包初始的位置
     img.style.position = this.options.position;
     var startTop = parseInt(Math.random()*10+(-10))
     var startLeft = parseInt(Math.random()*containerWidth);
     //移动的位置
     var moveLeft = parseInt(Math.random()*containerWidth+(-30));
     var t=parseInt(Math.random() * 1000+1200);
     this.evnAnimation({'startLeft':startLeft, 'startTop':startTop, 'moveLeft':moveLeft,'moveTop':containerHeight},t);
 }
 /*添加元素到主内容上*/
 RedEnvelope.prototype.evnAnimation =  function (posObject,time){
     $(this.options.containerClass).children('img:first').css({'left':posObject.startLeft,'top':posObject.startTop});
     $(this.options.containerClass).children('img:first').animate(
         {
             'left':posObject.startLeft-posObject.moveLeft,
             'top':posObject.moveTop
         },
         time,
         'linear',
         function(){
             $(this).remove();
         }
     );
     

html部分

<div class="redEnv-contain">
</div>

<script>
	setInterval(RedEnvelope,500);
</script>