javascript动画系列之模拟滚动条
作者：小火柴的蓝色理想
本文主要介绍了js动画模拟滚动条的实现原理以及分享了通过滚动条实现的几个应用的实例代码:1.通过移动滚动条来实现数字的加减;2.通过拖动滚动条来实现元素尺寸的变化，以改变元素宽度为例;3.通过拖动滚动条来实现内容滚。需要的朋友一起来看下吧
前面的话
当元素内容溢出元素尺寸范围时，会出现滚动条。但由于滚动条在各浏览器下表现不同，兼容性不好。所以，模拟滚动条也是很常见的应用。本文将详细介绍滚动条模拟
原理介绍
滚动条模拟实际上和元素模拟拖拽类似。仅仅通过范围限定，使元素只可以在单一方向上拖拽
<div id="box" style="height: 200px;width: 16px;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;">
<div id="test" style="height: 60px;width: 16px;background-color:#555;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<script>
test.onmousedown = function(e){
e = e || event;
var that = this;
var disY = e.clientY - this.offsetTop;
document.onmousemove = function(e){
e = e || event;
var T = e.clientY - disY;
if(T < 0){T = 0;}
var TMax = parseInt(box.style.height) - that.offsetHeight;
if(T > TMax){T = TMax;}
that.style.top = T + 'px';
}
document.onmouseup = function(){
document.onmousemove = null;
//释放全局捕获
if(test.releaseCapture){test.releaseCapture();}
}
//IE8-浏览器阻止默认行为
if(test.setCapture){test.setCapture();}
//阻止默认行为
return false;
}
</script>
通过将上面代码封装成函数，可以实现横向和纵向两种滚动条
<div id="box1" style="height: 200px;width: 16px;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;">
<div id="test1" style="height: 60px;width: 16px;background-color:#555;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<div id="box2" style="height: 16px;width: 200px;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;">
<div id="test2" style="height: 16px;width: 60px;background-color:#D62929;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<script>
function scrollbar(obj,str){
obj.onmousedown = function(e){
e = e || event;
var that = this;
//x轴方向
if(str == 'x'){
var disX = e.clientX - this.offsetLeft;
//否则为y轴方向
}else{
var disY = e.clientY - this.offsetTop;
}
document.onmousemove = function(e){
e = e || event;
if(str == 'x'){
var L = e.clientX - disX;
if(L < 0){L = 0;}
var LMax = parseInt(obj.parentNode.style.width) - that.offsetWidth;
if(L > LMax){L = LMax;}
that.style.left = L + 'px';
}else{
var T = e.clientY - disY;
if(T < 0){T = 0;}
var TMax = parseInt(obj.parentNode.style.height) - that.offsetHeight;
if(T > TMax){T = TMax;}
that.style.top = T + 'px';
}
}
document.onmouseup = function(){
document.onmousemove = null;
//释放全局捕获
if(obj.releaseCapture){obj.releaseCapture();}
}
//IE8-浏览器阻止默认行为
if(obj.setCapture){obj.setCapture();}
//阻止默认行为
return false;
}
}
scrollbar(test1);
scrollbar(test2,'x')
</script>
应用
下面来介绍通过滚动条实现的几个应用
数字加减
通过移动滚动条来实现数字的加减。比例关系为：
滚动条已移动距离/滚动条可移动距离= 数字当前值/数字最大值
<div id="box" style="height: 16px;width: 200px;display:inline-block;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;">
<div id="test" style="height: 16px;width: 60px;background-color:#D62929;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<span id="result">0</span>
<script>
function scrollbar(obj,str,max){
obj.onmousedown = function(e){
e = e || event;
var that = this;
//比例系数
var ratio;
//x轴方向
if(str == 'x'){
var disX = e.clientX - this.offsetLeft;
ratio = max/(this.parentNode.offsetWidth - this.offsetWidth);
//否则为y轴方向
}else{
var disY = e.clientY - this.offsetTop;
ratio =max/(this.parentNode.offsetHeight - this.offsetHeight);
}
document.onmousemove = function(e){
e = e || event;
if(str == 'x'){
var L = e.clientX - disX;
if(L < 0){L = 0;}
var LMax = parseInt(obj.parentNode.style.width) - that.offsetWidth;
if(L > LMax){L = LMax;}
that.style.left = L + 'px';
result.innerHTML = Math.round(ratio * L);
}else{
var T = e.clientY - disY;
if(T < 0){T = 0;}
var TMax = parseInt(obj.parentNode.style.height) - that.offsetHeight;
if(T > TMax){T = TMax;}
that.style.top = T + 'px';
result.innerHTML = Math.round(ratio * T);
}
}
document.onmouseup = function(){
document.onmousemove = null;
//释放全局捕获
if(obj.releaseCapture){obj.releaseCapture();}
}
//IE8-浏览器阻止默认行为
if(obj.setCapture){obj.setCapture();}
//阻止默认行为
return false;
}
}
scrollbar(test,'x',100);
</script>
元素尺寸
通过拖动滚动条来实现元素尺寸的变化，以改变元素宽度为例。比例关系为：
滚动条已移动距离/滚动条可移动距离= 元素当前宽度/元素最大宽度
<div id="box" style="height: 16px;width: 200px;display:inline-block;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;">
<div id="test" style="height: 16px;width: 60px;background-color:#D62929;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<span id="result" style="width: 1px;height: 50px;background-color:pink;display:inline-block;"></span>
<script>
function scrollbar(obj,str,max){
obj.onmousedown = function(e){
e = e || event;
var that = this;
//比例系数
var ratio;
//x轴方向
if(str == 'x'){
var disX = e.clientX - this.offsetLeft;
ratio = max/(this.parentNode.offsetWidth - this.offsetWidth);
//否则为y轴方向
}else{
var disY = e.clientY - this.offsetTop;
ratio =max/(this.parentNode.offsetHeight - this.offsetHeight);
}
document.onmousemove = function(e){
e = e || event;
if(str == 'x'){
var L = e.clientX - disX;
if(L < 0){L = 0;}
var LMax = parseInt(obj.parentNode.style.width) - that.offsetWidth;
if(L > LMax){L = LMax;}
that.style.left = L + 'px';
result.style.width = Math.round(ratio * L) + 'px';
}else{
var T = e.clientY - disY;
if(T < 0){T = 0;}
var TMax = parseInt(obj.parentNode.style.height) - that.offsetHeight;
if(T > TMax){T = TMax;}
that.style.top = T + 'px';
result.style.width = Math.round(ratio * T) + 'px';
}
}
document.onmouseup = function(){
document.onmousemove = null;
//释放全局捕获
if(obj.releaseCapture){obj.releaseCapture();}
}
//IE8-浏览器阻止默认行为
if(obj.setCapture){obj.setCapture();}
//阻止默认行为
return false;
}
}
scrollbar(test,'x',100);
</script>
内容滚动
通过拖动滚动条来实现内容滚动，比例关系为：
滚动条已移动距离/滚动条可移动距离= 内容已移动距离/内容可移动距离
<div id="box" style="height: 200px;width: 16px;display:inline-block;background-color:#F5F5F5;border-radius:10px;box-shadow:inset 0 0 6px rgba(0,0,0,0.3);position:relative;vertical-align:middle;">
<div id="test" style="height: 60px;width: 16px;background-color:#D62929;box-shadow:inset 0 0 6px rgba(0,0,0,.3);border-radius:10px;position:absolute;"></div>
</div>
<span id="result" style="width: 100px;height: 200px;background-color:pink;display:inline-block;line-height:30px;vertical-align:middle;position:relative;overflow:hidden;"><div id="resultIn" style="position:absolute;top:0;">测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br>测试文字<br></div></span>
<script>
function scrollbar(obj,str){
var max = result.offsetHeight - resultIn.offsetHeight;
obj.onmousedown = function(e){
e = e || event;
var that = this;
//比例系数
var ratio;
//x轴方向
if(str == 'x'){
var disX = e.clientX - this.offsetLeft;
ratio = max/(this.parentNode.offsetWidth - this.offsetWidth);
//否则为y轴方向
}else{
var disY = e.clientY - this.offsetTop;
ratio =max/(this.parentNode.offsetHeight - this.offsetHeight);
}
document.onmousemove = function(e){
e = e || event;
if(str == 'x'){
var L = e.clientX - disX;
if(L < 0){L = 0;}
var LMax = parseInt(obj.parentNode.style.width) - that.offsetWidth;
if(L > LMax){L = LMax;}
that.style.left = L + 'px';
resultIn.style.top = Math.round(ratio * L) + 'px';
}else{
var T = e.clientY - disY;
if(T < 0){T = 0;}
var TMax = parseInt(obj.parentNode.style.height) - that.offsetHeight;
if(T > TMax){T = TMax;}
that.style.top = T + 'px';
resultIn.style.top = Math.round(ratio * T) + 'px';
}
}
document.onmouseup = function(){
document.onmousemove = null;
//释放全局捕获
if(obj.releaseCapture){obj.releaseCapture();}
}
//IE8-浏览器阻止默认行为
if(obj.setCapture){obj.setCapture();}
//阻止默认行为
return false;
}
}
scrollbar(test,'y');
</script>
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