json data

json_data.js

var data = [
  {type: "a", income: 1},
  {type: "a", income: 1},
  {type: "e", income: 1},
  {type: "c", income: 1},
  {type: "d", income: 1},
  {type: "d", income: 1},
  {type: "d", income: 1},
];

var total = {};

for(i=0; i < data.length; i++){
  if (total[data[i].type] == undefined) {
    total[data[i].type] = 0;
  }
  total[data[i].type] = total[data[i].type] + data[i].income;
}

console.log(total.a);
console.log(total.c);
console.log(total.d);