function sumFind(arr,num){
            let differ = {}; 
            for(let i=0,len=arr.length;i<len;i++){
                r = num - arr[i];
                if(differ[r]){
                    console.log(true)
                }else{
                    differ[arr[i]] = true;
                }
            }
            return console.log(false);
            
        }
        sumFind([1,2,3,4],9);   //false
        sumFind([1,2,3,4],6);   //true