js 统计字符串或者数组的出现次数

var arr = 'abcabcab'
        var obj = {};
        for (var i = 0; i < arr.length; i++) {
            var key = arr[i];
            if (obj[key]) {
                obj[key]++;
            } else {
                obj[key] = 1;
            }
        }
        console.log(obj)