"HTML5 canvas ctx.fillText无法实现换行"

var c = $(&#39;#c&#39;)[0].getContext(&#39;2d&#39;);c.font = &#39;12px Courier&#39;;alert(c);var str = &#39;first line second line...&#39;;var a = 30;var b = 30;var lineheight = 15;var lines = str.split(&#39;&#39;);for (var j = 0; j<lines.length; j++)c.fillText(lines[j], a, b + (j*lineheight) );

// for canvas<canvas id="c" width="200" height="200"></canvas>

canvas {   background-color: #FFCE9E;}