Merge two objects with the same ID

If the only key that the objects have in common is id and you are sure that the value will always be the same, then just iterate over the properties of the objects and add the values to the third object: / p>

var a1 = {
	id: 1,
	qtde: 2
};
var a2 = {
	id: 1,
	nome: 'teste'
};
var a3 = {}

Object.keys(a1).forEach(function(key) {
	a3[key] = a1[key];
});

Object.keys(a2).forEach(function(key) {
	a3[key] = a2[key];
});

document.write(JSON.stringify(a3));

Given that JavaScript reference objects, you have two paths:

• add properties to the original object
• create an object with the properties of others (without changing the originals)

To add, you can do a function to combine (merge ) these objects.

function mergeInto(source, target) {
    Object.keys(source).forEach(function(key) {
        target[key] = source[key];
    });
}

In this case, the function does not need return because the target object is changed by reference.

Example: link

To keep the originals , as indicated by the response from @tayllan , you have to create a third object and to add features of both. In this case it might be so, and the function would already have to have return :

function mergeObjects(sourceA, sourceB) {
    var obj = {};
    var keys = Object.keys(sourceA).concat(Object.keys(sourceB));
    keys.forEach(function(key) {
        if (sourceA.hasOwnProperty(key)) obj[key] = sourceA[key];
        if (sourceB.hasOwnProperty(key)) obj[key] = sourceB[key];
    });
    return obj;
}
var c = mergeObjects(a, b); // Object {id: 1, nome: "teste", qtde: 2}

Example: link