var arr = [{name:'a',num:1},{name:'a',num:2},{'name':'b',num:3}],result=[];
function addObjnum(arr, result ) {
for(let i =0; i< arr.length; i++){
let flag = true;
for(let j = 0; j < result.length; j++){
if(arr[i].name == result[j].name){
flag = false;
result[j].num = result[j].num + arr[i].num;
};
};
if(flag){
result.push(arr[i]);
};
};
return result;
};
console.log(addObjnum(arr,result));