javascript数组根据key值value相加

let arr = [{
  num1: 100,
  num2: 100
}, {
  num1: 100,
  num2: 100
}, {
  num1: 100,
  num2: 100,
  num3: 200
}, {
  num1: 100,
  num2: 100,
  num3: 130
}]
let newArr = [], obj = {};

arr.forEach(item => {
  for(let key in item) {
  	let value = item[key];
  	key in obj ? (obj[key] += value) : (obj[key] = value)
  
  }
})

for(let i in obj) {
  let o = {};
  o[i] = obj[i];
  newArr.push(o)
}
console.log(newArr)
//0: {num1: 400}
//1: {num2: 400}
//2: {num3: 330}