Merging JSON objects with value comparison

Question

I need to merge two JSON objects.

First object:

var objectA = {
  "UUID1": {
    "user": {
      "ID": "1"
    }
  },
  "UUID2": {
    "user": {
      "ID": "2"
    }
  },
  "UUID3": {
    "user": {
      "ID": "3"
    }
  }
}

Second object:

var objectB = {
  "UUID4": {
    "user": {
      "ID": "4"
    }
  },
  "UUID5": {
    "user": {
      "ID": "3"
    }
  },
  "UUID6": {
    "user": {
      "ID": "2"
    }
  }
}

Expected result:

{
  "UUID1": {
    "user": {
      "ID": "1"
    }
  },
  "UUID2": {
    "user": {
      "ID": "2"
    }
  },
  "UUID3": {
    "user": {
      "ID": "3"
    }
  },
  "UUID4": {
    "user": {
      "ID": "4"
    }
  }
}

The trick is, the UUID will differ, but the primary key is the user ID. So, I need to compare the user IDs and keep only one UUID.

Is there a clever way on how to approach this? Nested loops using Object.keys(objectX).forEach did not work for me well :(

Thank you!

Did you try https://stackoverflow.com/q/9134649/3365113 – TechGirl Sep 13 '17 at 15:52 — TechGirl, Sep 13 '17 at 15:52
Yes, but I can't use jQuery I'm afraid. – flaesh Sep 13 '17 at 15:53 — flaesh, Sep 13 '17 at 15:53

score 1 · Accepted Answer · answered Sep 13 '17 at 15:56

You can just create custom function to handle this for you. Something like this:

var objectA = {
  "UUID1": {"user": {"ID": "1"}},
  "UUID2": {"user": {"ID": "2"}},
  "UUID3": {"user": {"ID": "3"}}
}

var objectB = {
  "UUID4": {"user": {"ID": "4"}},
  "UUID5": {"user": {"ID": "3"}},
  "UUID6": {"user": {"ID": "2"}}
}

function merge() {
  var result = {};
  var ids = [];
  for (var i = 0; i < arguments.length; i++) {
    for (var uuid in arguments[i]) {
      if (~ids.indexOf(arguments[i][uuid].user.ID)) {
        continue;
      }
      result[uuid] = arguments[i][uuid];
      ids.push(arguments[i][uuid].user.ID);
    }
  }
  return result;
}

var merged = merge(objectA, objectB);
console.log(merged);

Thanks a lot, I've finally used this version to solve my problem! — flaesh, Sep 14 '17 at 07:23

score 1 · Answer 2 · answered Sep 13 '17 at 16:00

You could take a hash table for remembering the inserted ID and build a new object out of the given objects.

var objectA = { UUID1: { user: { ID: "1" } }, UUID2: { user: { ID: "2" } }, UUID3: { user: { ID: "3" } } },
    objectB = { UUID4: { user: { ID: "4" } }, UUID5: { user: { ID: "3" } }, UUID6: { user: { ID: "2" } } },
    hash = Object.create(null),
    result = [objectA, objectB].reduce(function (r, o) {
        Object.keys(o).forEach(function (k) {
            if (!hash[o[k].user.ID]) {
                hash[o[k].user.ID] = true;
                r[k] = o[k];
            }
        });
        return r;
    }, {});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Great answer, too! Sadly, I can only accept one as "answered" and @codtex was just a bit faster with his. Thanks a lot! — flaesh, Sep 14 '17 at 07:24

Merging JSON objects with value comparison

2 Answers2