How to change object value within an array of objects with one from another array of objects?

Question

Considering the two arrays bellow:

let aaa = [{label: "nu", angle: 5}, {label: "na", angle: 3}]
let bbb= [{label: "nu", angle: 2}, {label: "na", angle: 6}]

How can I add the value on the angle key from one object with the corresponding one from the next array of objects and return one object or the other.

the result should be:

let ccc= [{label: "nu", angle: 7}, {label: "na", angle: 9}]

I have no idea how to solve this

Do items with same label have the same index in both arrays? Or can they be in random positions? Can label repeat in array? — adiga
– adiga, Commented May 31, 2019 at 18:02
I cannot guarantee that the items will have the same index in both arrays. The [tag: label] will not repeat.. it has to be unique — freebiker
– freebiker, Commented May 31, 2019 at 18:09

Fraction · Accepted Answer · 2019-05-31 18:05:56Z

1

You can use Array.reduce() and Array.findIndex() like this:

let aaa = [{label: "nu", angle: 5}, {label: "na", angle: 3}];
let bbb= [{label: "nu", angle: 2}, {label: "na", angle: 6}];

const ccc = [...aaa, ...bbb].reduce((acc, a) => {
  const i = acc.findIndex(o => o.label === a.label);

  if(i === -1) { acc.push(a); return acc; }
  
  acc[i].angle += a.angle;
  return acc;      
 }, []);
 
 console.log(ccc);

edited May 31, 2019 at 18:05

answered May 31, 2019 at 17:59

Fraction

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