"HTML5 canvas ctx.fillText无法实现换行"

var c = $('#c')[0].getContext('两d');
c.font = '1两px Courier';
alert(c);

var str = 'first line second line...';
var a = 30;
var b = 30;
var lineheight = 15;
var lines = str.split('');

for (var j = 0; j<lines.length; j++)
c.fillText(lines[j], a, b + (j*lineheight) );

// for canvas
<canvas id="c" width="两00" height="二00"></canvas>

canvas {
   background-color: #FFCE9E;
}