很low的四位验证码实现

<html>
    <head>
        <meta charset="utf-8">
    </head>
    <body>
        <input type="text" id="codeIn"><br>
        <span id="codebox">AAAA</span>
        <button type="button" id="codec">看不清换一张</button>
    </body>
    <script>
        let codeIn = document.querySelector("#codeIn"),
            codebox = document.querySelector("#codebox"),
            codec = document.querySelector("#codec");
            /*
                queryCode
                @param:none
                @rerurn:none
            */
           function queryCode(){
               let area = 'akjgf301290987tfhcn29';
               let result = '';
               for(let i=0; i<4; i++)
               {
                    let ran = Math.round(Math.random()*area.length-1);
                    result += area[ran];
               }
               codebox.innerHTML = result;
           }
           codec.onclick = function(){
               queryCode();
           }
           codeIn.onblur = function(){
               let val = codeIn.value,
                    code = codebox.innerHTML;
                    if(val.toLowerCase() === code.toLowerCase())
                    {
                        alert("验证成功");
                    }
                    else{
                        codeIn.value = '';
                        alert("验证失败，请重新输入");
                        queryCode();
                    }
           }
    </script>
</html>
原文地址：https://www.cnblogs.com/angle-xiu/p/11329339.html