<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.div {
position: absolute;
left: calc(50% - 50px);
top: calc(50% - 50px);
width: 100px;
height: 100px;
background: red;
}
</style>
</head>
<body>
<div class="div"></div>
<script src="mTween.js"></script>
<script>
{
let div = document.querySelector(".div");
let speedX = 0;
let speedY = 0;
let timer = 0;
/*
可以获得焦点的元素，才可以使用 keydown
*/
css(div,"translateX",0);
css(div,"translateY",0);
window.addEventListener("keydown",(e)=>{
switch(e.keyCode){
case 37:
// 左
speedX = -2;
break;
case 38:
// 上
speedY = -2;
break;
case 39:
// 右
speedX = 2;
break;
case 40:
// 下
speedY = 2;
break;
}
if(!timer){
timer = requestAnimationFrame(move);
}
});
window.addEventListener("keyup",()=>{
cancelAnimationFrame(timer);
speedX = 0;
speedY = 0;
timer = 0;
})
function move(){
let nowX = css(div,"translateX");
let nowY = css(div,"translateY");
css(div,"translateX",nowX += speedX);
css(div,"translateY",nowY += speedY);
timer = requestAnimationFrame(move);
}
}
</script>
</body>
</html>
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