How to Merge Objects in TypeScript
October 27, 2023
In TypeScript, merging objects is a common operation that can be achieved in various ways, depending on the desired outcome and the nuances of the merge. This guide will walk you through several methods of merging objects in TypeScript, highlighting their strengths and differences.
Object Spread Operator
The spread operator (
...) is a handy ES6 feature that allows for the creation of shallow copies of objects and arrays. When it comes to merging objects, you can use the spread operator to combine two or more objects into one.
Note: If properties from
obj2 have the same key, the latter object's value will override the former's.
Object.assign() is a method that was introduced in ES6 to copy values of all enumerable properties from one or more source objects to a target object.
Note: Like the spread operator, properties from later sources will overwrite those of earlier ones.
The methods above only perform shallow merges. If nested objects are present, they'll be overwritten rather than merged. For a deep merge, a custom function is often required.
Type Intersections for Merging Object Types
In TypeScript, if you're looking to merge types of objects (rather than the objects themselves), you can use type intersections.
While type intersections can create merged types, be cautious of overlapping property names as they may result in never types or other undesirable unions.
Utility Types for Merging
TypeScript also provides utility types that can assist with merging. One of the commonly used utility types is
Partial<T>, which makes all properties of type
In this example, the
mergeWithDefault function can accept a partial version of
A and merge it with the default values.
By leveraging TypeScript and ES6+ features, you can efficiently merge objects in a variety of ways. Always remember to choose the merging strategy that aligns best with your specific requirements.
How to fix the "not all code paths return a value" issue in TypeScript
Working with WebSockets in Node.js using TypeScript
Type Annotations Can Only Be Used in TypeScript Files
Guide to TypeScript Recursive Type
How to Configure Knex.js with TypeScript