What is the difference between Object.assign and Object.merge in JavaScript?

Table of Contents

• Introduction
• What is Object.assign?
  • Definition
  • Characteristics
  • Example
• What is Object.merge?
  • Definition
  • Characteristics
  • Example (using Lodash)
• Key Differences
• Conclusion

Introduction

In JavaScript, Object.assign and Object.merge are both used to combine objects, but they have distinct behaviors and use cases. While Object.assign is a standard method, Object.merge is not part of the official JavaScript specification but is commonly found in libraries. Understanding the differences can help in choosing the right approach for object manipulation.

What is Object.assign?

Definition

Object.assign is a built-in method that copies the values of all enumerable own properties from one or more source objects to a target object. It returns the target object.

Characteristics

• Shallow Copy: It performs a shallow copy, meaning it only copies properties at the first level. Nested objects are not cloned, but referenced.
• Mutates Target: It modifies the target object and can overwrite existing properties.

Example

What is Object.merge?

Definition

Object.merge is not a standard JavaScript method; it is typically found in libraries like Lodash or can be custom-implemented. Its purpose is to combine multiple objects into one, often providing additional features compared to Object.assign.

Characteristics

• Deep Merge (in libraries): Many implementations perform a deep merge, meaning nested objects are also merged, rather than referenced.
• Non-standard: As it is not part of the ECMAScript standard, its behavior can vary based on the library or custom implementation.

Example (using Lodash)

Key Differences

1. Standardization:
   • Object.assign: A standard method available in all modern JavaScript environments.
   • Object.merge: Not a standard method; relies on external libraries or custom implementations.
2. Merge Type:
   • Object.assign: Performs a shallow copy. Nested objects are not deeply merged.
   • Object.merge: Often provides deep merging capabilities (depends on implementation).
3. Mutation:
   • Object.assign: Mutates the target object.
   • Object.merge: Behavior can vary; some implementations create a new object, while others may mutate the target.
4. Use Cases:
   • Object.assign: Suitable for straightforward property copying and shallow merges.
   • Object.merge: Better for complex merging scenarios where nested objects need to be combined.

Conclusion

In conclusion, Object.assign and Object.merge serve different purposes in object manipulation in JavaScript. While Object.assign is a reliable method for shallow copying properties, Object.merge (when available) can provide more advanced merging capabilities. Understanding their differences helps developers choose the appropriate method for their specific needs.