What's the way to merge properties of two JavaScript objects?

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1

I'm looking to merge two simple JavaScript objects during runtime. For instance, I want to achieve something like this:

var obj1 = { food: 'pizza', car: 'ford' }
var obj2 = { animal: 'dog' }

obj1.merge(obj2);


//obj1 should now include three properties: food, car, and animal

Is there an existing method for doing this? I don't require recursion or merging of functions, just a merging of properties on flat objects.

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2

Hey!

Use Object.assign to merge objects:

var obj1 = { food: 'pizza', car: 'ford' };
var obj2 = { animal: 'dog' };

Object.assign(obj1, obj2);
// obj1 is now { food: 'pizza', car: 'ford', animal: 'dog' }

Done!

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3

When you want to combine JavaScript objects quickly at runtime, you can utilize the spread operator for a clean and efficient approach. This method allows you to merge objects in a simple and elegant way without needing additional functions or methods.

Here’s how you can merge two objects, obj1 and obj2, into obj1:

var obj1 = { food: 'pizza', car: 'ford' };
var obj2 = { animal: 'dog' };

obj1 = { ...obj1, ...obj2 };
// obj1 is now { food: 'pizza', car: 'ford', animal: 'dog' }

The spread operator ... efficiently combines the properties of obj2 into obj1. This maintains the original objects’ simplicity while expanding their properties. This approach is straightforward, efficient, and avoids unnecessary complexity.

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4

To merge two JavaScript objects at runtime without introducing excessive complexity, the Object.entries() along with forEach() loops can be used to manually assign properties. This approach not only provides clarity in understanding each step of the merge process but also allows for fine-tuned control over the operation, should additional logic be necessary.

Below is an example of how this can be done:

var obj1 = { food: 'pizza', car: 'ford' };
var obj2 = { animal: 'dog' };

Object.entries(obj2).forEach(([key, value]) => {
  obj1[key] = value;
});

// obj1 is now { food: 'pizza', car: 'ford', animal: 'dog' }
console.log(obj1);

Explanation:

  1. Object.entries(): This method returns an array of a given object’s own enumerable property [key, value] pairs, which are then traversed with forEach().

  2. forEach(): This method iterates over each [key, value] pair from obj2, allowing you to assign each pair to obj1. It offers an easy path to handle deeper customizations during merge operations, if necessary in future use cases.

  3. Assignment: Each entry from obj2 is subsequently assigned to obj1, ensuring that all keys and values from obj2 are properly transferred to obj1.

By following this approach, not only do you successfully merge two objects, but you also implement a method that can be easily extended for further customization.