This question explores JavaScript and addresses practical considerations related to: How can I prevent a JavaScript function from modifying its input object?

How can I prevent a JavaScript function from modifying its input object?

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

Post this Question & Answer:

How can I prevent a JavaScript function from modifying its input object?

Asked on Feb 10, 2026

Answer

Previous Question Next Question

To prevent a JavaScript function from modifying its input object, you can create a shallow copy of the object using Object.assign or the spread operator. Here's a simple example using the spread operator.

<!-- BEGIN COPY / PASTE -->
        function processObject(input) {
            const copy = { ...input };
            // Modify the copy as needed
            copy.newProperty = 'newValue';
            return copy;
        }

        const original = { key: 'value' };
        const result = processObject(original);

        console.log(original); // { key: 'value' }
        console.log(result);   // { key: 'value', newProperty: 'newValue' }
        <!-- END COPY / PASTE -->

Additional Comment:

The spread operator `{ ...input }` creates a shallow copy of the input object.
The original object remains unchanged, as modifications are applied to the copy.
For deep cloning (nested objects), consider using libraries like Lodash or structured cloning methods.
Always test your code to ensure the copy behaves as expected.

✅ Answered with JavaScript best practices.

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

How can I prevent a JavaScript function from modifying its input object?

Asked on Feb 10, 2026

Answer

Real Questions. Clear Answers.