1function combu(s){
2var buff = [];
3var res = [];
4for (i=0;i<s.length;i++){
5    buff = [s[i]];
6    var index=0;
7    while(res[index]){
8        buff.push(''+res[index]+s[i]);
9        index++;
10    }
11    res = res.concat(buff);
12}
13return res;
14}
15
16combu('abc');

1 function combString(str){
2     var lenStr = str.length;
3     var result = [];
4     var indexCurrent = 0;
5
6     while(indexCurrent < lenStr){
7         var char = str.charAt(indexCurrent);
8         var x;
9         var arrTemp = [char];
10
11         for(x in result) {
12             arrTemp.push(""+result[x]+char);
13         }
14         result = result.concat(arrTemp);
15
16         indexCurrent++;
17     }
18
19     return result;
20}
21
22console.log(combString("abc"));