<div class="v_code">
        <div class="code_show">
            <span class="code" id="checkCode"></span>
            <a id="linkbt">看不清换一张</a>
        </div>
        <div class="input_code">
            <label for="inputCode">验证码：</label>
            <input type="text" id="inputCode" />
            <span id="text_show"></span>
        </div>
        <input id="Button1" type="button" value="确定" />
 </div>
<script>
    // 1.生成验证码
    // 6位数  0-9 a-f  随机生成6位 内容必须是0-9 a-f 字符串
    // 数组 下标 0、1、2……    从数组当中 随机下标 0-15位

    // 2.进行验证 点击确定时，进行对比
    
    window.onload = function(){
        var res = getCode();
        function getCode(){
            var arr = ['0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'];
            var str = '';
            for(var i = 0;i<6;i++){
                var num = Math.round(Math.random()*(15-0)+0);
                str += arr[num];
            }
            return str;
        }
        document.getElementById('checkCode').innerText = res;
        // 点击事件
        document.getElementById('linkbt').onclick = function(){
            document.getElementById('checkCode').innerText = getCode();
        }


        // 提交进行对比
        document.getElementById('Button1').onclick = function(){
            var code = document.getElementById('checkCode').innerText;
            var inputCode = document.getElementById('inputCode').value;
            if(code != inputCode){
                alert('您输入的验证码不正确');
                document.getElementById('inputCode').value = '';
                return false;
            }
        }
    }

</script>
<style>
    .v_code {
        width: 600px;
        margin: 0 auto;
    }
    .v_code>input {
        width: 60px;
        height: 36px;
        margin-top: 10px;
    }
    .code_show {
        overflow: hidden;
    }

    .code_show span {
        display: block;
        float: left;
        margin-bottom: 10px;
    }

    .code_show a {
        display: block;
        float: left;
        margin-top: 10px;
        margin-left: 10px;
    }

    .code {
        font-style: italic;
        background-color: #f5f5f5;
        color: blue;
        font-size: 30px;
        letter-spacing: 3px;
        font-weight: bolder;
        float: left;
        cursor: pointer;
        padding: 0 5px;
        text-align: center;
    }

    #inputCode {
        width: 100px;
        height: 30px;
    }
    
    a {
        text-decoration: none;
        font-size: 12px;
        color: #288bc4;
        cursor: pointer;
    }

    a:hover {
        text-decoration: underline;
    }
    .form{
        width: 300px;
        height: 300px;
        background-color: #eee;
    }
</style>