前端滑块验证

1.前端页面应用滑块验证可以防止页面频繁向后台请求数据；

2.主要用到js事件：

   onmousedown()   鼠标按下时响应

   onmousemove()   鼠标移动时响应

   onmouseup()        鼠标弹起时响应

3.获取页面距离：

   e.clientx

   obj.offsetwidth

   obj.offsetleft

4.代码：

html:

<div class="box">
      <div class="txt">滑块验证</div>
      <div class="btn">&gt;&gt;</div>
      <div class="bg"></div>
</div>

css:

*{
        -webkit-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;
    }
    .box{
        position: relative;
        width:300px;
        height:30px;
        background-color: #ccc;
        margin:20px auto;
        font-size:14px;
        line-height:30px;
        box-sizing:border-box;
        z-index:1;
    }

    .txt{
        position: absolute;
        left: 50%;
        top:0;
        transform: translatex(-50%);
        color:blue;
        z-index:3;
    }

    .btn{
        position: absolute;
        top:0;
        left: 0;
        width:40px;
        height:30px;
        border:1px solid #ccc;
        background-color: #fff;
        text-align: center;
        line-height: 30px;
        cursor: move;
        box-sizing: border-box;
        z-index:4;
    }

    .bg{
        position: absolute;
        left: 0;
        top:0;
        width:0;
        height:30px;
        background-color:green;
        box-sizing: border-box;
        z-index:2;
    }

js:

window.onload = function(){
        var box = document.queryselector(".box"),
            txt = document.queryselector(".txt"),
            btn = document.queryselector(".btn"),
            bg  = document.queryselector(".bg"),
            end = false;

        btn.onmousedown = function(e){
            var e = e ||  window.event;
            var point = e.clientx -  box.offsetleft;
            btn.onmousemove = function(e){
                var movew = e.clientx - box.offsetleft - point;
                btn.style.left = movew + "px";
                bg.style.width = movew + "px";

                if(btn.offsetleft<=0){
                    btn.style.left = "0";
                }

                if(btn.offsetleft>=(box.clientwidth - btn.clientwidth)){
                    btn.style.left = box.clientwidth - btn.clientwidth
                    txt.innerhtml = "验证完成";
                    btn.onmousemove = null;
                    btn.onmousedown = null;
                    end = true;
                }
            }

            btn.onmouseup = function(){
                btn.onmousemove = null;
                if(!end){
                    btn.style.left = "0";
                    bg.style.width = "0";
                }
            }
        }
    }

5.显示