随机验证码

    <script type="text/javascript">
        var charCode = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';


        function getRandom(n,m){
            n = Number(n);
            m = Number(m);
            return Math.round(Math.random()*(m-n)+n)
        }

        getRandom(1,61);

        function getCode(){
            let str = '';
            for(let i=0;i<4;i++){
                var code = charCode.charAt(getRandom(1,61));
                str+=code;
            }
            console.log(str);
        }