What is the most efficient way to deep clone an object in JavaScript?

Leveraging Modern APIs and Trusted Libraries for Deep Cloning

Deep cloning an object creates an entirely new object with the same structure and values, ensuring changes to the cloned object don’t affect the original. Over the years, developers have used various techniques, but modern JavaScript now provides a built-in structured cloning algorithm that is often the most efficient and reliable option.

1. Using structuredClone() (Modern and Native)

As of Node.js 17+ and supported in modern browsers, structuredClone() is a built-in function that deep clones a wide variety of objects, including arrays, objects, and more complex data structures, without needing external libraries:

const original = { a: 1, b: { c: 2 } };
const clone = structuredClone(original);

console.log(clone); // { a: 1, b: { c: 2 } }
console.log(original.b === clone.b); // false (deeply cloned)

Key Points:

• Handles many built-in types, including Dates, Maps, and Sets.
• Doesn’t rely on hacks or extra dependencies.
• Limited browser support (Chrome 98+, Firefox 94+, Safari 15.4+) and Node.js 17+ but increasingly available in modern environments.

2. Using JSON.parse(JSON.stringify()) (Legacy Approach)

A long-standing hack for deep cloning simple objects is to convert them to a JSON string and then parse them back into a new object:

const original = { a: 1, b: { c: 2 } };
const clone = JSON.parse(JSON.stringify(original));

Key Points:

• Only works for data that can be represented in JSON (no functions, undefined, or complex types like Date or Set).
• Loses object type information (e.g., Date objects become strings).
• Might be slower and less flexible than modern approaches.

3. Using Libraries (e.g., Lodash)

If you’re working in a production environment where you need robust deep cloning and structuredClone() is not available or insufficient, a library like Lodash provides a cloneDeep() function:

import _ from "lodash";

const original = { a: 1, b: { c: 2 } };
const clone = _.cloneDeep(original);

Key Points:

• Comprehensive and battle-tested solution.
• Handles various edge cases.
• Requires an external dependency.

4. Custom Clone Functions or Other Tools

For specialized scenarios (e.g., custom classes, circular references, or large data structures), you may implement a custom cloning function or use specialized utilities. However, this is typically more complex and unnecessary with the availability of structuredClone() and well-maintained libraries.

Choosing the Most Efficient Way

• Use structuredClone() whenever possible in modern environments. It’s native, efficient, and handles a wide range of data types correctly.
• Fallback to JSON.parse(JSON.stringify()) for simple data if you can’t rely on newer environments, but be aware of its limitations.
• Use a library like Lodash when you need robust, widely compatible deep cloning and cannot rely on modern JavaScript features or are dealing with complex data structures.

Strengthening Your JavaScript Fundamentals

Deep cloning objects is just one of many everyday coding tasks in JavaScript. Building a strong foundation in core concepts makes tasks like this simpler and helps you choose the most appropriate solution for your use-case:

• Grokking JavaScript Fundamentals: Ideal for beginners or those refining their skills, this course covers essential language features, data structures, and best practices.

In Summary

The most efficient way to deep clone an object in JavaScript today is to use the native structuredClone() function, provided you’re in an environment that supports it. Otherwise, consider the data types and constraints of your scenario to decide between JSON.parse(JSON.stringify()), a library like Lodash, or a custom solution.