javascript - How to get all properties of the second array of objects when comparing with the first?

Question

I am using JavaScript with lodash and have two array of objects as follows:

objArr1 = [{'x': 1, 'y': 2, 'z': 3}, {'x': 10, 'y': 20, 'z': 30}, {'x': 100, 'y': 200, 'z': 300}, {'x': 1000, 'y': 2000, 'z': 3000}, {'x': 10000, 'y': 20000, 'z': 30000}]

objArr2 = [{'x': 1, 'y': 2, 'a': 5}, {'x': 10, 'y': 20, 'a': 6}, {'x': 100, 'y': 200, 'a': 9}]

I am using the matching key as 'x' and I am able to get:

_.intersectionBy(objArr1, objArr2, 'x')

[{'x': 1, 'y': 2, 'z': 3}, {'x': 10, 'y': 20, 'z': 30}, {'x': 100, 'y': 200, 'z': 300}]

However, I also need to get the 'a' property in the second array of objects.

e.g.

[{'x': 1, 'y': 2, 'z': 3, 'a': 5}, {'x': 10, 'y': 20, 'z': 30, 'a': 6}, {'x': 100, 'y': 200, 'z': 300, 'a': 9}]

Couldn't seem to figure out using lodash.

Please help! Thanks!

question from:https://stackoverflow.com/questions/65894808/how-to-get-all-properties-of-the-second-array-of-objects-when-comparing-with-the

Answer 1

This would be relatively simple to roll yourself without lowdash. The following combineArrays function takes a key and any number of arrays. It iterates over those arrays and puts any values into an object indexed by the desired key. Finally, Object.values grabs the final desired array.

const objArr1 = [{'x': 1, 'y': 2, 'z': 3}, {'x': 10, 'y': 20, 'z': 30}, {'x': 100, 'y': 200, 'z': 300}, {'x': 1000, 'y': 2000, 'z': 3000}, {'x': 10000, 'y': 20000, 'z': 30000}];

const objArr2 = [{'x': 1, 'y': 2, 'a': 5}, {'x': 10, 'y': 20, 'a': 6}, {'x': 100, 'y': 200, 'a': 9}];

function combineArrays(key, ...arrs) {
  const result = {};
  const counts = {};
  arrs.forEach(arr => {
    arr.forEach(el => {
      result[el[key]] = { ...result[el[key]], ...el }; 
      counts[el[key]] = (counts[el[key]] || 0) + 1;
    });
  });
  return Object.values(result).filter(obj => 
    counts[obj[key]] > 1
  );
}

console.log(
  combineArrays("x", objArr1, objArr2)
);