JS生成随机数的各种函数

/*
*@desc:生成随机字符串
*@remark:toString方法可以接收一个基数作为参数的原理，这个基数从2到36封顶。如果不指定，默认基数是10进制
*/
function generateRandomAlphaNum(len) {
    var rdmString = "";
    for (; rdmString.length < len; rdmString += Math.random().toString(36).substr(2));
    return rdmString.substr(0, len);
}

//JS生成GUID函数,类似.net中的NewID(); 
function S4() {
    return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
}

function NewGuid() {
    return (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
}

//JS生成GUID函数,类似.net中的NewID(); 
function newGuid() {
    var guid = "";
    for (var i = 1; i <= 32; i++) {
        var n = Math.floor(Math.random() * 16.0).toString(16);
        guid += n;
        if ((i == 8) || (i == 12) || (i == 16) || (i == 20))
            guid += "-";
    }
    return guid;
}

/*
*@desc:生成随机字符串
*@demo:console.log(ranStr());
*/
;(function(){
    //数字0-9，大写字母，小写字母，ASCII或UNICODE编码（十进制），共62个
    var charCodeIndex = [[48,57],[65,90],[97,122]];
    var charCodeArr = [];

    function getBetweenRound(min,max){
        return Math.floor(min+Math.random()*(max-min));
    };

    function getCharCode(){
        for(var i=0,len=3;i<len;i++){
            var thisArr = charCodeIndex[i];
            for(var j=thisArr[0],thisLen=thisArr[1];j<=thisLen;j++){
                charCodeArr.push(j);
            }
        }
    }

    function ranStr(slen){
        slen = slen || 20;
        charCodeArr.length<62 && getCharCode();

        var res = [];
        for(var i=0;i<slen;i++){
            var index = getBetweenRound(0,61);
            res.push(String.fromCharCode(charCodeArr[index]));
        }
        return res.join(‘‘);
    };

    this.ranStr = ranStr;
})();