Merging two Javascript objects into key, array pairs

Question

If I have two objects:

const obj1 = {
 "1,1" : "hello",
}

and

 const obj2 = {
 "1,1" : "hi",
}

what would be the easiest way to merge them into:

obj3 = {
"1,1": ["hello", "hi"],
} 

can i use the spread operator here? thanks!

Answer 1

An alternative is using the function reduce.

const obj1 = {"1,1" : "hello"},
      obj2 = {"1,1" : "hi"},
      obj3 = [obj1, obj2].reduce((a, c) => {
                Object.keys(c).forEach(k => (a[k] || (a[k] = [])).push(c[k]));
                return a;
             }, {});

console.log(obj3);

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Answer 2

a simple way to do this would be to use the internal for (.. in ...) of javascript : e.g.

obj1 = {1 : 2};
obj2 = {1 : 3};
obj3 = {};

for (element1 in obj1) {
 for (element2 in obj2) { 
   if (element1 == element2) {
        obj3[element1] = [];
        obj3[element1].push(obj1[element1]);
        obj3[element1].push(obj2[element2]);
    }
   }
  }
//result : obj3 = {1 : [2,3]}

but then what if obj1 = {"1,1" : 2, 1.1 : 3} or obj1 = {"1,1" : [1,2,3,4]} ? You really need to "well define" your requirement, but this should be a pretty good start.

Answer 3

var obj1 = {
    a: 1,
    b: 2
};

var obj2 = {
    a: 12,
    c: 20
};

console.log(merge(obj1, obj2));

function merge(obj1, obj2) {

    var obj3 = {};

    Object.keys(obj1).forEach(function(key) {
        pushIntoObj3(key, obj1[key]);
    });

    Object.keys(obj2).forEach(function(key) {
        pushIntoObj3(key, obj2[key]);
    });

    function pushIntoObj3(key, val) {
        if (!obj3[key]) {
            obj3[key] = [];
        }
        obj3[key].push(val);
    }

    return obj3;
}

OUTPUT :

{
  "a": [ 1, 12 ],
  "b": [ 2 ],
  "c": [ 20 ]
}