The flatMap() method transforms each element of an array using a mapping function and flattens the result into a new array. It applies the function to every element, avoiding empty ones, and preserves the original array.

Syntax:

let A = array.flatMap(function callback(current_value, index, Array)) {
// It returns the new array's elements.
}

Parameters:

• current_value: It is the input array element.
• index:
  • It is optional.
  • It is the index of the input element.
• Array: 
  
  • It is optional.
  • It is used when an array map is called.

Return Values:

It returns a new array whose elements are the return value of the callback function.

Example 1: In this example the flatMap() method doubles and squares each number in the array, creating a new flattened array, making complex transformations manageable.

const numbers = [1, 2, 3, 4];
const doubledAndSquared = 
	numbers.flatMap(num => [num * 2, num ** 2]);
console.log(doubledAndSquared);

[
  2, 1, 4,  4,
  6, 9, 8, 16
]

Example 2: In this example, the flatMap() method is employed to process an array of sentences. The callback function, sentence => sentence.split(' '), is applied to each sentence, splitting it into an array of words. The flatMap() method then flattens these arrays into a single-dimensional array of words.

const sentences = 
	["Hello world", "How are you?", "JavaScript is fun"];
const words = 
	sentences.flatMap(sentence => sentence.split(' '));
console.log(words);

[ 'Hello', 'world', 'How', 'are', 'you?', 'JavaScript', 'is', 'fun' ]

We have a complete list of Javascript Array methods, to check those please go through this Javascript Array Complete reference article.

Supported Browser:

• Google Chrome
• Edge 
• Firefox
• Opera
• Safari