js不用split分割数组实现取出重复字符

<script>
var str = ',1,2,3,4,5,6,6,3,10,112,55,8,7,15,9,12,12,';
var arr = str.match(/[,，]/g);
var sumCount = arr.length;
var count = 0;
var nextCount = str.indexOf(",", count + 1);
var obj = [];
for (var i = 0; i < sumCount; i++) {
var nexNum = str.indexOf(",", nextCount);
var num_str = str.substring(count, nexNum)+ ",";
if (str.indexOf(num_str) >= 0 && str.indexOf(num_str, str.indexOf(num_str) + 1) >= 0
&& obj.indexOf(num_str.replace(/,/g, "")) < 0)
obj.push(num_str.replace(/,/g, ""));
count = str.indexOf(",", count + 1);
nextCount = str.indexOf(",", count + 1);
}
console.info(obj)
</script>