<canvas id="canvas" width="400" height="400" style="border:1px red solid;">

<script>

function obj(id){return document.getElementById(id);}

vas cs = boj("canvas");

var ctxt = cs.getContext("2d");

ctxt.begingPath();

ctxt.moveTo(50,50);

ctxt.lineTo(150,50);

ctxt.stroke();

</script>

注：如有补充或有错之处，请指出，谢谢！