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Lodash _.chain


lodash is a popular open-source JavaScript utility library that provides a wide range of methods to simplify working with arrays, strings, objects, and functions. One of the most powerful methods in lodash is _.chain(). This method allows developers to chain multiple lodash methods together to transform data in a clean and concise way.

_.chain() creates a lodash wrapper object that allows the application of chainable sequence of methods to any value. Instead of applying a series of different methods on a value, such as an array or object, separately, _.chain() offers a functional paradigm that allows developers to create a chain of methods that results in the desired outcome for that value.

The advantage of using _.chain() over regular lodash methods is that it provides flexibility and simplicity in manipulating data. Each method in the chain processes the result of the previous method, allowing for easy data transformations. This formatting is done in a way that promotes readability in terms of coding.

One major benefit of _.chain() is that it helps to eliminate complex code repetition, thus reducing the possibility of human error. _.chain() acts as an abstraction layer allowing developers to deal with transformations in a simple and clear manner.

The chain method returns a wrapped object, which means that in order to get the final result, you need to call .value() which will execute the methods in the chain and return the final value. It's essential to call .value() at the end of the chain as the execution of the chain methods is deferred until a final result can be computed.

Here's an example of how you can use _.chain() to filter, map, sort, and reduce the values of an array:

const users = [
  { name: 'John', age: 27 },
  { name: 'Jane', age: 21 },
  { name: 'Mike', age: 32 },
  { name: 'Lisa', age: 19 }

const result = _.chain(users)
  .filter(user => user.age >= 21)
  .map(user => ({ fullName: `${} Doe`, age: user.age }))
  .reduce((acc, user) => acc + user.age, 0)

// result: 59

Here, we first filter the array to exclude any users under the age of 21. We then map each user object to a new object that includes their full name and age. Next, we sort the array in ascending order of age. Finally, we use the reduce() method to calculate the sum of ages of all users, with an initial value of 0.

In summary, _.chain() is a powerful method that allows developers to perform complex data transformations in a simple and readable manner. Its functional paradigm eliminates complex code repetition, resulting in reduced human error while promoting maintainable, scalable code.