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What is the difference between shallow copy and deep copy in JavaScript?

Asked on Jul 27, 2025

Answer

In JavaScript, a shallow copy duplicates the top-level properties of an object, while a deep copy duplicates all nested objects, creating independent copies. Here's how you can create each type of copy:

<!-- BEGIN COPY / PASTE -->
        // Shallow copy using Object.assign
        const original = { a: 1, b: { c: 2 } };
        const shallowCopy = Object.assign({}, original);

        // Deep copy using JSON methods
        const deepCopy = JSON.parse(JSON.stringify(original));
        <!-- END COPY / PASTE -->

Additional Comment:

A shallow copy (using Object.assign) copies only the top-level properties. Changes to nested objects in the original will affect the shallow copy.
A deep copy (using JSON methods) creates a completely independent copy, but it only works for JSON-safe objects (e.g., no functions, undefined, or symbols).
For complex objects, consider using libraries like Lodash for deep cloning.
Always choose the appropriate method based on your data structure and requirements.

✅ Answered with JavaScript best practices.

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

What is the difference between shallow copy and deep copy in JavaScript?

Asked on Jul 27, 2025

Answer

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