怎樣去除js鍵的引號(hào)

    function  duplicates(arr) {
        var obj = {};
        var newArr = [];
        for (var i in arr){
            if(obj[arr[i]]){
                obj[arr[i]]++;
            }
            else{
                obj[arr[i]]=1;
            }
        }
        Object.keys(obj).forEach(function(key){
            if(obj[key]==1){
                newArr.push(key);
            }
        });
        console.log(newArr);
        var str = newArr.join('');
        console.log(str);
        var newarr2 = [];
        newarr2 = str.split('');
        console.log(newarr2);

    }
    duplicates([1,2,3,3,6,6,5]);