SOURCE

function writeDocument(variable) {
    document.write(variable + "<br/>");
} 

writeDocument("最大值最小值-----------------");
writeDocument("最大值；" + Math.max(1,3,9,10,18,999));
writeDocument("最小值；" + Math.min(1,3,9,10,18,999));

writeDocument("生成4位随机验证码--------------------");

function generateVerifyCode(length){
    var strLetterNumber = "012345678ABCDEFGHIJKLMNOPQRST";
    var code = "";
    for(var i = 0; i < length; ++i){
        var randomNumber = Math.floor(Math.random() * strLetterNumber.length);
        code = code + strLetterNumber.charAt(randomNumber);
    }

    return code;
}

writeDocument(generateVerifyCode(4));
writeDocument(generateVerifyCode(5));
writeDocument(generateVerifyCode(6));