How do I merge two objects in JavaScript?

How do I merge two objects in JavaScript?

You can use the Object.assign() method or the spread operator to merge two objects. For example:

// Using Object.assign() const obj1 = { a: 1, b: 2 }; const obj2 = { b: 3, c: 4 }; const merged = Object.assign({}, obj1, obj2);

// Using spread operator const mergedWithSpread = {...obj1, ...obj2};

Both will result in { a: 1, b: 3, c: 4 }.

What's the difference between Object.assign and the spread operator?

The main difference is that Object.assign() mutates the first object passed to it, while the spread operator creates a new object without modifying the original ones. Also, Object.assign() can only copy properties from one or more source objects to a target object, while the spread operator is more concise and easier to read.

Can I merge more than two objects?

Yes, you can merge multiple objects using both Object.assign() and the spread operator. For example:

// Using Object.assign() const merged = Object.assign({}, obj1, obj2, obj3);

// Using spread operator const mergedWithSpread = {...obj1, ...obj2, ...obj3};

Both will combine all properties from the objects into a new object.

What happens if there are duplicate keys?

If there are duplicate keys, the last object's value will overwrite the previous ones. For example, if obj1 has a key 'a' with value 1 and obj2 has 'a' with value 2, the merged object will have 'a' with value 2.