var c = canvas.getContext("2d");//get canvas 2d context

canvas including a proposed 3D context;

c.fillStyle("#ffffff");//rawing canvas background color

c.fillRectangle(sx,sy,ex,ey);//drawing a rectanle ,the (sx,sy) is start point,(ex,ey) is end point

c.font = "20px"//the canvas font size is 20 pixel

c.textBaseline = "top"//the text vertical position

c.fillText("Hello",100,100);//drawing a text to canvas,The three parameters of this method are text string,x position,y position

c.strokeStyle = "#ffffff";//set a color for the stroke(the border of the box)

c.strokeRect(0,0,100,100);//upper left x and y coordinates ,and the lower right x and y coordinates