<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>random</title>
</head>
<body>
    <input type="text"><span></span>
    <input type="button" id="random">
    <input type="button" id="submit" value="提交">
</body>
</html>
<script src="js/jquery-1.10.2.js"></script>
<script>
    // 创建数组
    var chars = [‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘, ‘G‘, ‘H‘, ‘I‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘];
    // 取出数组个数
    var len = chars.length - 1;
    // 生成随机整数
    var a = (Math.random() * len).toFixed();
    var b = (Math.random() * len).toFixed();
    var c = (Math.random() * len).toFixed();
    var d = (Math.random() * len).toFixed();
    // 取出数组中的值
    var A = chars[a];
    var B = chars[b];
    var C = chars[c];
    var D = chars[d];
    var str = A + " " + B + " " + C + " " + D;
    $(‘#random‘).val(str);
    $(‘input[id=submit]‘).click(function () {
        // 取到文本里的值
        var txt = $(‘input[type=text]‘).val();
        var btn = $(‘input[id=random]‘).val();
        var strs = "";
 
        // 循环添加空格
        for (var i = 0; i < txt.length; i++) {
            strs += txt[i] + ‘ ‘;
        }
        // 判断验证
        if (strs.trim().toLowerCase() === btn.trim().toLowerCase()) {
            alert(true)
        } else {
            $(‘span‘).html(‘验证码错误‘)
        }
    })
</script>