String.prototype.trim = function () {
    var str = this.toString()
    if (str == '' || !str.length) return str;
    return str.replace(/^\s*((.|[\r\n])*[^\s])\s*$/,"$1");
}

function randomInt () {
    var st = 0;
    var en = 1;
    if (arguments.length == 2) {
        st = arguments[0];
        en = arguments[1];
    } else if (arguments.length == 1) en = arguments[0];
    return parseInt(st + Math.round(Math.random() * (en - st)));
}

String.prototype.random = function (length) {
    var str = '';
//	var ranges = {0:[48,57],1:[65,90],2:[97,122]};
    var ranges = new Array();
    ranges[0] = [48,57];
    ranges[1] = [65,90];
    ranges[2] = [97,122];
    for (var i=0; i<length; i++) { k = randomInt(2); str += String.fromCharCode(randomInt(ranges[k][0],ranges[k][1])); }
    return str;
}