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Lodash _.setWith


Introduction: The _.setWith() method is a utility function provided by the popular Lodash library, which provides a way to set the value of a property on an object or nested objects. This method is somewhat similar to the _.set() method, but with the added ability to customize the behavior when creating objects.

Syntax: The _.setWith() method has the following syntax.

_.setWith(object, path, value, customizer)

Parameters: The _.setWith() method accepts four parameters, which are described below.

  1. object: It is the object which we want to change.
  2. path: It is a string or an array that represents the path to the property which we want to set.
  3. value: It is the value that we want to set on the specified object's path.
  4. customizer: (Optional) It is a function that is used to customize the creation of the new object.

Return: _.setWith() method returns the modified object once the specified value has been set to the specified path.

Customizing the behavior of _.setWith(): The _.setWith() method provides a way to customize the creation of the new object. We can pass a customizer function to the _.setWith() method, which will be called for each new property that is created along the path.

The customizer function receives three arguments:

  1. The new object being created.
  2. The key of the new property.
  3. The value of the new property.

The customizer function should return the value that should be assigned to the new property. If it returns undefined, the default behavior will be used to create the new property.


const _ = require('lodash');

// Create an object const person = { name: { first: 'John', last: 'Doe' }, age: 25 };

// Using _.setWith to set the value _.setWith(person, 'name.middle', 'Smith', Object);

console.log(person); // { name: { first: 'John', middle: 'Smith', last: 'Doe' }, age: 25 }

In the above example, we have used _.setWith() to set a new property called 'middle' on the nested object 'name'. Since there is no 'middle' property on the 'name' object, it is created by the _.setWith() method.

Conclusion: The _.setWith() method is a versatile utility function provided by the Lodash library, which allows us to set the value of a property on an object or nested objects with the added ability to customize the creation of new objects. This method can be very useful in situations where we need to modify and manipulate complex nested data structures.