ts+canvas 实现代码雨

/**
 * 1.获取canvas dom
 * 2.获取屏幕可视宽高 赋值给 canvas
 * 3.创建绘制的字符和数组
 * 4.创建rain函数 设置默认背景 颜色 fillRect 的 坐标
 * 5.设置fillText 随机字符 
 * copy by 小满zs	
 * 
 */

let canvas = document.querySelector('#canvas') as HTMLCanvasElement;
let ctx = canvas.getContext('2d') as CanvasRenderingContext2D;

canvas.width = screen.availWidth

canvas.height = screen.availHeight

let str: string[] = 'CanvasRenderingContext2D'.split('')

let Arr = Array(Math.ceil(canvas.width / 10)).fill(0)


const rain = () => {
    ctx.fillStyle = 'rgba(0,0,0,0.05)'//填充背景颜色
    ctx.fillRect(0, 0, canvas.width, canvas.height)
    ctx.fillStyle = '#0f0'
    Arr.forEach((item, index) => {
        ctx.fillText(str[Math.floor(Math.random() * str.length)], index * 10, item + 15)
        Arr[index] = item > canvas.height || item > 10000 * Math.random() ? 0 : item + 15
    })
}

setInterval(rain, 40)