textBbaseline for aling of text baseline to font baseline on a Canvas

gctx.textBaseline='top';

top: Top of the em Square is at text baseline.
hanging: Hanging baseline is at text baseline.
middle: Middle of the em Suare is at text baseline .
alphabetic: alphabetic baseline is at text baseline
ideographic: ideographic baseline is at text baseline.
bottom: bottom of the bounding box is at text baseline

var my_canvas=$('#my_canvas').get(0)
var gctx = my_canvas.getContext("2d");
gctx.font='38px Arial';
gctx.fillStyle='#00FF00';
gctx.textBaseline='top';
gctx.fillText('JQP349 gjpqy',100,100)

textBaseline : on Canvas