Lodash Difference Between Extend Assign And Merge

Lodash library is a powerful and versatile tool that can greatly simplify your JavaScript coding experience. Among its many functions, three key methods in Lodash are `_.extend()`, `_.assign()`, and `_.merge()`. While they may seem similar at first glance, understanding the nuances between them can greatly benefit your development process. Let's dive into the differences between these three methods to help you leverage Lodash to its fullest potential.

1. _.extend()
The `_.extend()` method in Lodash is used to copy the properties of one or more source objects to a target object. It modifies the target object by adding properties from the source objects. This method takes multiple source objects as arguments and copies their properties into the target object. One thing to note is that `_.extend()` mutates the target object directly.

Example:

var target = { a: 1 };
var source = { b: 2 };
_.extend(target, source);
console.log(target); // Output: { a: 1, b: 2 }

2. _.assign()
On the other hand, `_.assign()` is also used to copy the values of all enumerable own properties from one or more source objects to a target object. The key difference with `_.assign()` is that it does not deeply clone objects, meaning that it performs a shallow copy. It overwrites the target object properties with source object properties, and it does not modify the source objects.

Example:

var target = { a: 1 };
var source = { b: 2 };
_.assign(target, source);
console.log(target); // Output: { a: 1, b: 2 }

3. _.merge()
Lastly, `_.merge()` is used to recursively merge the properties of two or more objects. This method deeply merges source objects into the target object, handling nested objects with ease. It differs from `_.assign()` and `_.extend()` as it does not simply overwrite properties but instead merges them.

Example:

var target = { a: { b: 1 } };
var source = { a: { c: 2 } };
_.merge(target, source);
console.log(target); // Output: { a: { b: 1, c: 2 } }

In summary, while all three methods in Lodash - `_.extend()`, `_.assign()`, and `_.merge()` - have their use cases, understanding their distinctions is crucial for effectively manipulating objects in your JavaScript projects. So, the next time you're working with Lodash and need to copy or merge objects, remember these differences to choose the right method for your needs.