Using Optional Chaining with Array.find in JavaScript: A Guide to Safe Value Mutations

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The Problem: Mutating Values with Optional Chaining

Consider the following JavaScript code snippet where we want to find an object in an array and then change one of its properties based on a condition:

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

At first glance, it seems logical to use optional chaining to avoid errors when the find method doesn’t return a match. However, this results in an error. Why does this happen?

What’s Going Wrong?

When you try to execute the code above, you might encounter a TypeError. This is because using optional chaining in the assignment context leads to the following interpretation:

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

In this case, the JavaScript engine treats the expression on the left of = as an undefined target when entry is not found, thus throwing an error. To clarify, optional chaining is excellent for accessing properties, but it cannot be used for assigning values.

The Solution: Safely Mutating Values

Using Nullish Coalescing

The syntax below ensures that if no matching element is found, a new empty object is used instead, allowing you to avoid runtime errors:

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

Breaking Down the Solution:

Safe Assignment: The code attempts to assign 50 to the value property. If the element is not found, it writes to an empty object—which doesn’t cause any error as there’s no violation in assignment.

Summary

While optional chaining enhances the safety of property access, it’s important to remember that it doesn’t support assignment operations. Instead, you can use the nullish coalescing operator to ensure that safe mutations can take place without throwing an error. This pattern not only helps you avoid bugs but also keeps your code clean and concise.

In conclusion, learning how to combine techniques effectively can lead to better handling of JavaScript's nuances. By applying the outlined solution, you can safely manipulate values in arrays without running into unnecessary complications.