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How can I ensure a function in JavaScript remains pure when dealing with objects that need modification?

Asked on Dec 07, 2025

Answer

To ensure a function remains pure when dealing with objects, you should avoid modifying the original object and instead return a new object with the desired changes. This can be achieved using techniques like object spread syntax or `Object.assign`.

<!-- BEGIN COPY / PASTE -->
        function updateObject(original, changes) {
            return { ...original, ...changes };
        }

        const original = { a: 1, b: 2 };
        const updated = updateObject(original, { b: 3 });

        console.log(original); // { a: 1, b: 2 }
        console.log(updated);  // { a: 1, b: 3 }
        <!-- END COPY / PASTE -->

Additional Comment:

The function "updateObject" uses the object spread syntax to create a new object.
The original object remains unchanged, ensuring the function is pure.
The function returns a new object with the modifications applied.
This approach helps maintain immutability in your code.

✅ Answered with JavaScript best practices.

Ask any question about JavaScript here... and get an instant response.

How can I ensure a function in JavaScript remains pure when dealing with objects that need modification?

Asked on Dec 07, 2025

Answer

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