js return indicie of string of ceritn sub string

1function getIndicesOf(searchStr, str, caseSensitive) {
2    var searchStrLen = searchStr.length;
3    if (searchStrLen == 0) {
4        return [];
5    }
6    var startIndex = 0, index, indices = [];
7    if (!caseSensitive) {
8        str = str.toLowerCase();
9        searchStr = searchStr.toLowerCase();
10    }
11    while ((index = str.indexOf(searchStr, startIndex)) > -1) {
12        indices.push(index);
13        startIndex = index + searchStrLen;
14    }
15    return indices;
16}