console 命令行工具 X clear

console

function draw(offset){
    const canvas = document.getElementById('canvas')
    const ctx = canvas.getContext('2d')
    ctx.clearRect(0,0,canvas.width, canvas.height)
    ctx.setLineDash([4,2])
    ctx.lineDashOffset = offset
    ctx.strokeRect(10,10,100,100)
}

let offset = 100; 
setInterval(()=>{
    offset--
    if(offset<0) offset = 100;
 draw(offset)
},50)

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