shadow not work

[prinsun]

var canvas = createCanvas();
var ctx = canvas.getContext('2d');

ctx.fillStyle = '#0ff';
ctx.fillRect(0, 0, canvas.width, canvas.height);

ctx.shadowBlur = 4.0;
ctx.shadowColor = 'red';
ctx.shadowOffsetX = 2.0;
ctx.shadowOffsetY = 2.0;
ctx.lineWidth = 2;
ctx.strokeStyle = 'yellow';
ctx.strokeRect(20, 60, 100, 100);
ctx.fillStyle = 'yellow';
ctx.font = '40px Georgia';
ctx.fillText('Hello Wolrd', 20, 210);