用tween.js实现一个简单的返回顶部
<!DOCTYPE html>
<html lang="en">
<head>
<title>Document</title>
<style>
* {
padding: 0;
margin: 0;
}
body {
height: 2000px;
}
.box {
position: fixed;
bottom: 50px;
right: 50px;
color: red;
}
</style>
</head>
<body>
<div class="box" id="box">toTOp</div>
<script>
var box = document.getElementById('box')
box.onclick = function() {
let doc = document.body.scrollTop || document.documentElement.scrollTop
// console.log(doc)
Math.animation(doc, 0, 200, 'Circ.easeIn', function(value) {
if (document.documentElement.scrollTop) {
document.documentElement.scrollTop = value
} else {
document.body.scrollTop = value
}
})
}
/*
* Tween.js
* t: current time（当前时间）；
* b: beginning value（初始值）；
* c: change in value（变化量）；
* d: duration（持续时间）。
* you can visit 'http://easings.net/zh-cn' to get effect
*/
var Tween = {
Linear: function(t, b, c, d) {
return c * t / d + b
},
Quad: {
easeIn: function(t, b, c, d) {
return c * (t /= d) * t + b
},
easeOut: function(t, b, c, d) {
return -c * (t /= d) * (t - 2) + b
},
easeInOut: function(t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t + b
return -c / 2 * ((--t) * (t - 2) - 1) + b
}
},
Cubic: {
easeIn: function(t, b, c, d) {
return c * (t /= d) * t * t + b
},
easeOut: function(t, b, c, d) {
return c * ((t = t / d - 1) * t * t + 1) + b
},
easeInOut: function(t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t + b
return c / 2 * ((t -= 2) * t * t + 2) + b
}
},
Quart: {
easeIn: function(t, b, c, d) {
return c * (t /= d) * t * t * t + b
},
easeOut: function(t, b, c, d) {
return -c * ((t = t / d - 1) * t * t * t - 1) + b
},
easeInOut: function(t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b
return -c / 2 * ((t -= 2) * t * t * t - 2) + b
}
},
Quint: {
easeIn: function(t, b, c, d) {
return c * (t /= d) * t * t * t * t + b
},
easeOut: function(t, b, c, d) {
return c * ((t = t / d - 1) * t * t * t * t + 1) + b
},
easeInOut: function(t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b
return c / 2 * ((t -= 2) * t * t * t * t + 2) + b
}
},
Sine: {
easeIn: function(t, b, c, d) {
return -c * Math.cos(t / d * (Math.PI / 2)) + c + b
},
easeOut: function(t, b, c, d) {
return c * Math.sin(t / d * (Math.PI / 2)) + b
},
easeInOut: function(t, b, c, d) {
return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b
}
},
Expo: {
easeIn: function(t, b, c, d) {
return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b
},
easeOut: function(t, b, c, d) {
return (t == d) ? b + c : c * (-Math.pow(2, -10 * t / d) + 1) + b
},
easeInOut: function(t, b, c, d) {
if (t == 0) return b
if (t == d) return b + c
if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b
return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b
}
},
Circ: {
easeIn: function(t, b, c, d) {
return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b
},
easeOut: function(t, b, c, d) {
return c * Math.sqrt(1 - (t = t / d - 1) * t) + b
},
easeInOut: function(t, b, c, d) {
if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b
return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b
}
},
Elastic: {
easeIn: function(t, b, c, d, a, p) {
var s
if (t == 0) return b
if ((t /= d) == 1) return b + c
if (typeof p === 'undefined') p = d * 0.3
if (!a || a < Math.abs(c)) {
s = p / 4
a = c
} else {
s = p / (2 * Math.PI) * Math.asin(c / a)
}
return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b
},
easeOut: function(t, b, c, d, a, p) {
var s
if (t == 0) return b
if ((t /= d) == 1) return b + c
if (typeof p === 'undefined') p = d * 0.3
if (!a || a < Math.abs(c)) {
a = c
s = p / 4
} else {
s = p / (2 * Math.PI) * Math.asin(c / a)
}
return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b)
},
easeInOut: function(t, b, c, d, a, p) {
var s
if (t == 0) return b
if ((t /= d / 2) == 2) return b + c
if (typeof p === 'undefined') p = d * (0.3 * 1.5)
if (!a || a < Math.abs(c)) {
a = c
s = p / 4
} else {
s = p / (2 * Math.PI) * Math.asin(c / a)
}
if (t < 1) return -0.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b
return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * 0.5 + c + b
}
},
Back: {
easeIn: function(t, b, c, d, s) {
if (typeof s === 'undefined') s = 1.70158
return c * (t /= d) * t * ((s + 1) * t - s) + b
},
easeOut: function(t, b, c, d, s) {
if (typeof s === 'undefined') s = 1.70158
return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b
},
easeInOut: function(t, b, c, d, s) {
if (typeof s === 'undefined') s = 1.70158
if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b
return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b
}
},
Bounce: {
easeIn: function(t, b, c, d) {
return c - Tween.Bounce.easeOut(d - t, 0, c, d) + b
},
easeOut: function(t, b, c, d) {
if ((t /= d) < (1 / 2.75)) {
return c * (7.5625 * t * t) + b
} else if (t < (2 / 2.75)) {
return c * (7.5625 * (t -= (1.5 / 2.75)) * t + 0.75) + b
} else if (t < (2.5 / 2.75)) {
return c * (7.5625 * (t -= (2.25 / 2.75)) * t + 0.9375) + b
} else {
return c * (7.5625 * (t -= (2.625 / 2.75)) * t + 0.984375) + b
}
},
easeInOut: function(t, b, c, d) {
if (t < d / 2) {
return Tween.Bounce.easeIn(t * 2, 0, c, d) * 0.5 + b
} else {
return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * 0.5 + c * 0.5 + b
}
}
}
}
/**
* [tween description]
* from 起始位置
* to 结束位置
* name 动画名字
* callback 动画结束后的回掉
*/
Math.tween = Tween
Math.animation = function(from, to, duration, name, callback) {
var tween = Math.tween || window.Tween
duration = duration || 300
name = name || 'Linear'
callback = callback || function() {}
if (!window.requestAnimationFrame) {
window.requestAnimationFrame = function(fn) {
return setTimeout(fn, 17)
}
}
if (!window.cancelAnimationFrame) {
window.cancelAnimationFrame = function(id) {
clearTimeout(id)
}
}
// 算法需要的几个变量
var start = 0
// during根据设置的总时间计算
var during = Math.ceil(duration / 17)
// 动画请求帧
var req = null
name = name.slice(0, 1).toUpperCase() + name.slice(1)
var arrKeyTween = name.split('.')
var fnGetValue
if (arrKeyTween.length == 1) {
fnGetValue = tween[arrKeyTween[0]]
} else if (arrKeyTween.length == 2) {
fnGetValue = tween[arrKeyTween[0]] && tween[arrKeyTween[0]][arrKeyTween[1]]
}
// 运动
var step = function() {
var value = fnGetValue(start, from, to - from, during)
start++
if (start <= during) {
callback(value)
req = requestAnimationFrame(step)
} else {
callback(to, true)
}
}
// 开始执行动画
step()
return function() {
return req
}
}
</script>
</body>
</html>
好处是可以自定义动画效果，用起来很方便，以上代码直接复制是可以运行的
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