<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>fold paper effect by gt-柯樂義</title>
<style>
#wrapper {
-webkit-perspective: 55cm;
-webkit-perspective-origin: 50% 50%;
text-align: center;
}
.paper {
position: relative;
height: 40px;
width: 5em;
margin: 0;
background-color: aqua;
-webkit-transition: -webkit-transform 1s linear;
}
</style>
<script type="text/javascript">
window.angel = 0;
window.timer;
function fold() {
var foldUp = document.getElementById("foldUp");
var foldDown = document.getElementById("foldDown");
var down = document.getElementById("down");
if (window.angel == 0) {
window.timer = setInterval(function() {
var diff = different(-1, 20);
console.log(foldUp.offsetTop)
move(foldUp, diff, 1);
move(foldDown, diff, 3);
move(down, diff, 4);
}, 40);
setTimeout(function() {
clearInterval(window.timer);
foldUp.style.top = "-20px";
foldDown.style.top = "-60px";
down.style.top = "-80px";
window.angel = -90;
}, 1030);
foldUp.style.webkitTransform = "rotateX(-90deg)";
foldDown.style.webkitTransform = "rotateX(90deg)";
} else if (angel == -90) {
window.timer = setInterval(function() {
var diff = different(1, 20);
console.log(foldUp.offsetTop)
move(foldUp, diff, 1);
move(foldDown, diff, 3);
move(down, diff, 4);
}, 40);
setTimeout(function() {
clearInterval(window.timer);
foldUp.style.top = "0";
foldDown.style.top = "0";
down.style.top = "0";
window.angel = 0;
}, 1030);
foldUp.style.webkitTransform = "rotateX(0deg)";
foldDown.style.webkitTransform = "rotateX(0deg)";
} else {
console.log(window.angel)
}
}
function positionValue(div, type) {// 得到css帶單位的值
var str = div.style[type];
str = str.substring(0, str.length - 2);
var value = parseInt(str);
if (isNaN(value)) {
value = 0;
}
return value;
}
function move(div, different, time) {
var top = positionValue(div, "top");
div.style.top = top + different * time + "px";
}
function different(direction, height) {
var lastAngel = window.angel;
window.angel += 3.6 * direction;
var different = Math
.ceil((Math.cos(window.angel / 180 * Math.PI) - Math
.cos(lastAngel / 180 * Math.PI))
* height * 100) / 100;
return different;
}
</script>
</head>
<body>
<div id="wrapper">
<div id="up" class="paper">
g
</div>
<div id="foldUp" class="paper">
n
</div>
<div id="foldDown" class="paper">
b
</div>
<div id="down" class="paper">
t
</div>
</div>
<button onclick=fold();>
fold
</button>
</body>
</html>
