How to merge properties of two JavaScript objects?
How to merge properties of two JavaScript objects?
Ask by ICSM Computer
Updated 04 Mar 2025
It is a common task in structured data handling to merge properties from two JavaScript objects. This can be done by a variety of different approaches depending on the type of merging required shallow or deep.
A very common way to achieve this is by using the spread operator(...), which has been used mainly in copying objects until now. When a property is found in both objects, the second object will replace the value in the first object. It is the most used method for shallow merging.
Another method is using
Object.assign(), which takes one or more source objects and merges them into a target object. The modifications occur to the target object, and this can be used to merge many objects. The means just provide a shallow merge; therefore, nested properties are not merged deeply but overridden.In more complicated scenarios with deep nested properties, a deep merge is needed. There is no native function for deep merging in JavaScript, but the many ways of triggering it include creating recursive functions or borrowing it through libraries, such as
Lodash'smerge function. The merging is guaranteed to deal with the nesting level.When merging some objects, it should be figured out how conflicting keys are resolved, references if they should be kept indebted to deep or shallow merging. Once the right one is chosen, you ensure efficiency in data handling while retaining any integrity.