var c = document.getElementById("myCanvas");//注意有双引号
var context = c.getContext("2d");
context.moveTo(0,0);
context.lineTo(200,100);
context.stroke();
var c = document.getElementById("myCanvas");//注意有双引号
var context = c.getContext("2d");
context.moveTo(0,0);
context.lineTo(200,100);
context.stroke();