动态画线问题 求高手

就是读取XML文件中的point 然后动态画出根据XML中点连成的线。要求在Canvas中画出
求高手啊。。本人找了个网上的例子是用span的下面是代码
function print(str) {
  //body.innerHTML+=str;
  body.insertAdjacentHTML("AfterBegin",str)
  //document.write(str)
  }
 function outPlot(x,y,w,h) {
  draw_num++;
  var span_id="span_"+draw_num;
  print('<span id="'+span_id+'"style="position:absolute;left:'+x+';top:'+y+';height:'+h+';width:'+w+';font-size:5px;background-color:'+color+'"></span>')
  var set_time=span_id+".style.display='none'";
  setTimeout(set_time,1000);
  }function draw()
          {
            if(x1<x2){
            outPlot(x1,y1,5,5);
            x1++;
            y1=y1+(y1-y2)/(x1-x2);
            }
          }调用函数setInterval("draw()",100);