java算法day5

一、功能描述

        使用canvas实现一个代码雨的功能，炫一个~~~

二、上码

html

 <canvas id="canvas"></canvas>

js

        let canvas = document.querySelector('canvas');
        let ctx = canvas.getContext('2d');
        // screen.availWidth:可视区域的宽度
        canvas.width = screen.availWidth;
        canvas.height = screen.availHeight;

        let str = 'zyk01010168'.split('');
        const px = 10;
        let arr = Array(Math.ceil(canvas.width / px )).fill(0)
        const rain = () => {
            //使用,0.05模糊，每次都重叠绘制。看出虚幻的效果
            ctx.fillStyle = 'rgba(0,0,0,0.05)';
            ctx.fillRect(0, 0, canvas.width, canvas.height);
            ctx.fillStyle = '#00FF00';
            arr = arr.map((ele,index) => {
                //横向间隔px的距离显示字母
                ctx.fillText(str[Math.floor(Math.random() * str.length)], index * px, ele + px);
                //修改纵向坐标
                return (ele > canvas.height || ele > 5000 * Math.random()) ? 0 : ele+ 10
            });
        }
        setInterval(rain, 40)