拖动滑块验证是现在的网站随处可见的，各式各样的拖动法都有。
下面实现的是某宝的拖动滑块验证：
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><style type="text/css">.drag{position: relative;width: 300px;height: 34px;background-color: #e8e8e8;line-height: 34px;}.bg{position: absolute;width: 40px;height: 100%;background-color: #7ac23c;}.text{position: absolute;width: 100%;margin: 0;text-align: center;}.btn{position: absolute;width: 40px;height: 32px;background: #fff url(data:image/png;base64,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) center no-repeat;border: 1px solid #ccc;cursor: pointer;}</style></head><body><div class="drag"><div class="bg"></div><p class="text">拖动滑块验证</p><div class="btn"></div></div><script>var $ = function(selector){return document.querySelector(selector);},box = $('.drag'),//容器 bg = $('.bg'),//绿色背景 text = $('.text'),//文字 btn = $('.btn'),//拖动按钮 done = false;//是否通过验证btn.onmousedown = function(e){var e = e || window.event;var posX = e.clientX - this.offsetLeft;btn.onmousemove = function(e){var e = e || event;var x = e.clientX - posX;this.style.left = x + 'px';bg.style.width = this.offsetLeft + 'px';// 通过验证if(x >= box.offsetWidth - btn.offsetWidth){done = true;btn.onmousedown = null;btn.onmousemove = null;text.innerHTML = '通过验证';}};document.onmouseup = function(){btn.onmousemove = null;btn.onmouseup = null;if(done)return;btn.style.left = 0;bg.style.width = 0;}};text.onmousedown = function(){return false;}</script></body></html>
由于是原生js实现的，因此没有加上动画效果，不然代码量太大。
代码简单，直接看下结构就明了了。
