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Learn how to update key values of JSON objects in an array effectively in Angular by avoiding unintended overwrites.
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How to Properly Update JSON Object Key Values in Angular Arrays

When working with arrays of JSON objects in Angular, you might face a common issue: updating the key values of those objects correctly while avoiding overwrites. This guide will guide you through the process of achieving the desired output when updating an array's key values using values from another array.

The Problem

Suppose you have the following data structure:

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

The goal is to update the age property of each object in the arr array using values from the ar array. However, you may encounter unexpected behavior, such as all objects in the array ending up with the last value of ar for the age property. Here’s an example of what could go wrong:

Example Code

Here’s the code that causes the issue:

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

Output

The output from the above code would look like this:

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

Expected Output

What we actually expect is:

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

The Solution

Understanding the Problem

The core issue arises because you’re directly modifying the age of the existing object e. When you push e into array, you’re adding the same reference to the object each time, causing all entries to reflect the last modification.

Creating New Objects

To solve this, you should create a new object each time instead of modifying and pushing the same reference. Here’s how:

Updated Code

You can change your function to look like this:

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

Explanation of Changes

New Object Creation: By creating a new object item that includes the properties you need, you prevent changes to the shared reference. This way, when you push it into array, each entry maintains its own age value as intended.

Conclusion

When updating JSON objects in an array with values from another array in Angular, it's crucial to create new objects rather than modifying existing ones directly. This small but significant change will ensure your output meets your expectations without unintended overwrites.

If you're faced with similar challenges in your Angular development journey, remember: always create a new reference when you want distinct instances!