随机组合排列的js或者jquery如何写?

代码如下：

function foo(chars) {
if (!chars.length) return;
var _foo = function(chars, tmp) {
for (i in chars) {
var ch = chars;
var t = tmp + ch[i];
var ch = delCharAt(chars, i);
if (ch.length < 1) {
alert(t);
} else {
_foo(ch, t);
}
}
};
_foo(chars, '');
}

function delCharAt(s, i) {
ss = '';
for (j in s) {
if (i != j) {
ss += s[j];
}
}
return ss;
}


foo('1234');