用H5的canvas做出弹幕效果

let canvas = document.getElementById('canvas');let ctx = canvas.getContext('2d');ctx.font = '20px Microsoft YaHei';          //字体、大小ctx.fillStyle = '#000000';                  //字体颜色ctx.fillText('canvas 绘制文字', 100, 100);   //文本，字体x,y坐标

ctx.measureText('文本宽度').width

ctx.clearRect(0, 0, width, height);