Скачать или смотреть How to Partially Copy Values from One Object to Another in JavaScript

Discover a simple way to partially copy values from one object to another in JavaScript using `Object.assign`. Learn how to avoid overwriting additional keys while updating existing values.
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Understanding Object Value Updates in JavaScript

In JavaScript, object manipulation is a common task. You may come across scenarios where you have two objects, and you wish to update one object with the values from another. This task can sometimes get tricky, especially when additional keys are involved.

Consider the following example: you have two objects, object1 and object2. The second object contains all the keys from the first object, along with some extra keys. Your goal is to update object2 using the values from object1 without touching the additional keys that are unique to object2.

The Problem:

You have:

[[See Video to Reveal this Text or Code Snippet]]

After the update, you want object2 to look like this:

[[See Video to Reveal this Text or Code Snippet]]

Notice that the value for key c remains untouched while the values for keys a and b are updated.

The Solution: Using Object.assign

The simplest way to achieve this in a compact manner is by using the Object.assign method. This method allows you to copy properties from one or more source objects to a target object. Here’s how it works:

Step-by-Step Implementation

Understanding Object.assign:

This method copies the values of all enumerable own properties from one or more source objects to a target object.

If the property already exists in the target, it will be overwritten.

Applying the Method:
You can use Object.assign to create a new object with properties combined from object2 and object1. You should pass object2 as the first argument followed by object1 to ensure that the values from object1 overwrite the existing keys in object2.

The Code Example

Here is the code that accomplishes this:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

We start by defining object1 and object2.

The Object.assign method is then invoked with three arguments:

An empty object {} which will hold the merged properties.

object2, from which we want to maintain all the original properties.

object1, which contains the properties we want to copy over and update.

Finally, we log the updatedObject to the console, which results in:

[[See Video to Reveal this Text or Code Snippet]]

Summary

Using Object.assign is a neat and efficient way to partially update one object with values from another without having to loop through each key-value pair. It allows you to keep any additional properties that may exist in the target object unaffected while updating existing properties.

By mastering this method, you can streamline your JavaScript code and make object handling much more manageable.