Lodash _.flatMapDepth() Method

Lodash is a JavaScript library that works on the top of underscore.js. Lodash helps in working with arrays, collection, strings, objects, numbers etc.

The _.flatMapDepth() method creates a flattened array of values by running each element in the given collection through the iteratee function. It recursively flattens the mapped results up to the given depth value. It is similar to the _.flatMap() method.

Syntax:

_.flatMapDepth( collection, iteratee, depth )

Parameters: This method accepts three parameters as mentioned above and described below:

• collection: It is the collection to iterate over.
• iteratee: It is the function that is invoked per iteration.
• depth: It is a number that specifies the maximum recursion depth. It is an optional parameter. The default value is 1.

Return Value: This method returns the new flattened array.

Example 1:

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = ([3, 4]);

// Using the _.flatMapDepth() method
let flat_map = _.flatMapDepth(users, duplicate, 2 )
function duplicate(n) {
  return [[[n, n]]];
}

// Printing the output
console.log(flat_map);

Output:

[ [ 3, 3 ], [ 4, 4 ] ]

Example 2:

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = (['q', 'r', 't', 'u']);

// Using the _.flatMapDepth() method
let flat_map = _.flatMapDepth(users, duplicate, 2 )
function duplicate(n) {
  return [[[n, n]]];
}

// Printing the output
console.log(flat_map);

Output:

[ [ 'q', 'q' ], [ 'r', 'r' ], [ 't', 't' ], ['u', 'u' ] ]