Canvas-矩形绘制-Day01

01矩形入门

02矩形进阶

03矩形高级

清屏

        //语法：ct.clearRect(x, y, width, hegiht)
        //canv.width,canv.height   自动获取画布的宽高
        ct.clearRect(0,0,canv.width,canv.height);