/*

*@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;

})();