web前端js中随机生成指定位数的字母数字、组合字符串可选择字母大小写

$rootScope.randomString = "";
$scope._getRandomString = function(len){
len = len || 32;
var $chars = 'ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678'; // 默认去掉了容易混淆的字符oOLl,9gq,Vv,Uu,I1
var maxPos = $chars.length;
var pwd = '';
var num = '';
for (i = 0; i < len; i++) {
pwd += $chars.charAt(Math.floor(Math.random() * maxPos));
num+=Math.floor(Math.random()*10);
}
pwd.toLowerCase();
$rootScope.randomString = pwd+num;
return pwd;
}