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Learn how to use React Hooks to efficiently add new properties to your state-managed arrays with practical examples.
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How to Push Elements into an Existing Array using React Hooks

Managing state in React, particularly when it comes to arrays, can sometimes be a challenge for developers, especially those who are new to React Hooks. If you possess an array and want to add new properties to the objects within that array, you're in the right place! In this post, we'll address a common scenario in React: pushing new properties into an existing array while utilizing Hooks efficiently.

The Problem at Hand

Let’s say you have an array defined to hold user information, like this:

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

You want to add a new property named online to the objects within the array. For example, after modification, your array should look like this:

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

If you are managing this array with state in a React component using Hooks (like so: const [defaultList, setDefaultList] = useState([]);), how do you accomplish this? Here’s how you can effectively do it.

Solutions for Adding Properties to an Array

1. Using .map()

One of the simplest and most functional approaches to adding properties to each object in an array is using the .map() method. This will create a new array with the updated objects.

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

How it works:

You iterate over each element (el) in defaultList.

For each element, you return a new object that includes all properties from el — thanks to the spread operator ...el — plus the new online property set to 'yes'.

2. Using .forEach() with Object.assign()

Another approach is to use the .forEach() method combined with Object.assign(). This modifies the original objects in place:

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

Understanding this approach:

The forEach() method iterates over each element in the array.

Within the loop, Object.assign() adds the new property online to the existing object el.

3. Using for..of

You could also use a for..of loop, which functions similarly to forEach():

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

Benefits of for..of:

It offers a clear and readable way to iterate over arrays.

Like forEach(), it mutates the original array objects.

Important Consideration: Mutation vs. Immutability

When working with arrays and state in React:

Immutability: The .map() method is preferable when you want to create a new state based on the previous state, as React recommends immutability for detecting changes.

Mutation: Both .forEach() and for..of methods mutate the original objects, which can lead to issues in state management and unintended side effects.

Conclusion

Adding new properties to an array of objects in React while using Hooks can be accomplished in several ways. Using .map() is the most React-friendly method as it maintains immutability, while both .forEach() and for..of can be useful depending on your specific needs.

Experiment with each approach to find what works best for you and aligns with your coding style!

Now you have the tools you need to effectively manage arrays in React. Happy coding!