input ['A:1','B:2','C:3','D:4','E:5','C:6','A:7','E:8'] => result { A: 8, B: 2, C: 9, D: 4, E: 13 }

//  결과 { A: 8, B: 2, C: 9, D: 4, E: 13 }
   var source = ['A:1','B:2','C:3','D:4','E:5','C:6','A:7','E:8'];
   var result = {};
   for(var i=0; i<source.length; i++) {
      var key = source[i].split(':')[0];
      var val = Number(source[i].split(':')[1]);
      if(result.hasOwnProperty(key)) { // 여기.. 
        result[key] = result[key] + val;
      } else {
        result[key] = val;
      }
   }
   console.log('result>>>', result);