Help me understand the lesson (JavaScript)

Question

https://www.sololearn.com/learn/JavaScript/2978/

So, I'm at the part where it talks about spread operators on objects, first it writes we can merge two objects like this:

Let obj1 = {.....}
Let obj2 = {.....}

Let mergedObj = {...obj1, ...obj2}

Then it writes trying to merge them like this wouldn't work:

Let obj1 = {.....}
Let obj2 = {.....}

Function merge(...arr){
return {...arr};
}

Let mergedObj = merge(obj1, obj2);

Which I thought was obvious anyway, and I don't even see why telling us that is even needed.

Then it writes we should use Object.assign to merge objects.

So should I use spread operator to merge objects or not? Am I the only one who thinks this lesson is very badly made?

Answer 1

function merge(...arr) {
return {...arr};
}

Now if you call it,
let mergedObj = merge(obj1, obj2);

The parameter arr becomes [obj1, obj2] #array
{...arr} therefore will be {
0: obj1,
1:obj2,
}

The function merge does not merge objects!

Rewrite the function like this
function(...objects) {
return Object.assign({}, ...objects);
}

Object.assign({}, ...objects) will give
Object.assign({}, obj1, obj2);

Don't be confused though. Spread is still helpful in merging objects like this
var obj3 = {...obj1, ...obj2}