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Lodash _.flatMapDeep() Method

  • Last Updated : 14 Sep, 2020

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

Syntax:

_.flatMapDeep( collection, iteratee )

Parameters: This method accepts two 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.

Return Value: This method returns the new flattened array.



Example 1:




// Requiring the lodash library 
const _ = require("lodash");
      
// Original array 
var users = (['aaa', 'bbb', 'ccc'
              'ddd', 'eee', 'fff']);
  
// Using the _.flatMapDeep() method
let flat_map =
  _.flatMapDeep(users,
    function duplicate(n) {
      return [[[n, n]]];
  }
)
  
// Printing the output 
console.log(flat_map);

Output:

[
  'aaa', 'aaa', 'bbb', 'bbb',
  'ccc', 'ccc', 'ddd', 'ddd',
  'eee', 'eee'
]

Example 2:




// Requiring the lodash library 
const _ = require("lodash"); 
      
// Original array 
var user1 = ([1, 2, 3, 4, 5, 6, 7]);
var user2 = (['a', 'b', 'c', 'd', 'e']);
  
// Using the _.flatMapDeep() method
let flat_map1 =
  _.flatMapDeep(user1,
    function makePattern(n) {
      return [[[n, n + "->"]]];
  }
)
   
let flat_map2 =
  _.flatMapDeep(user2,
    function makePattern(n) {
      return [[["<-" + n, n]]];
  }
)
  
// Printing the output 
console.log(flat_map1);
console.log(flat_map2);

Output:

[
  1, 1->, 2, 2->, 3, 3->,
  4, 4->, 5, 5->, 6, 6->,
  7, 7->
]
[
  '<-a', 'a', <-'b', 'b',
  '<-c', 'c', '<-d', 'd',
  '<-e', 'e'
]



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