JavaScript ---- Canvas扇形图封装

//原型var Canvas = function(ele,num){this.ele = ele;this.num = num;this.ctx = this.ele.getContext("2d");this.color = ["#21a74f","#b3e5f1","#3498db","#2ecc71","#f1c40f","#e67e22"];this.draw();}Canvas.prototype.draw=function(){var j=0,j1=0,j2=0,angle=0;var sum=0;for(var i=0;i<this.num.length;i++){sum=sum+this.num[i];}for(var i=0;i<this.num.length;i++){j=2*Math.PI*this.num[i]/sum;j2=j1+j;this.ctx.beginPath();this.ctx.fillStyle=this.color[i];this.ctx.arc(this.ele.width/2,this.ele.height/2,120,j1,j2,false);this.ctx.lineTo(this.ele.width/2,this.ele.height/2);this.ctx.closePath();this.ctx.fill();angle=j1+j/2;j1=j1+j;}}//实例调用var ele1=document.getElementById("can1");var num1=[100,300,300,500,200];var ele2=document.getElementById("can2");var num2=[100,300,300];var can1 = new Canvas(ele1,num1);var can2 = new Canvas(ele2,num2);