Introduction to lodash

lodash is a modern JavaScript utility library delivering modularity, performance & extras. It allows developers to work with arrays, numbers, objects, strings, etc., in an easier and more efficient way. Below are some key lodash functions you should know.

lodash API Examples

1. _.chunk

Creates an array of elements split into groups the length of size. If array can’t be split evenly, the final chunk will be the remaining elements.

  
  _.chunk(['a', 'b', 'c', 'd'], 2);
  // => [['a', 'b'], ['c', 'd']]
  

2. _.compact

Creates an array with all falsey values removed. The values false, null, 0, “”, undefined, and NaN are falsey.

  
  _.compact([0, 1, false, 2, '', 3]);
  // => [1, 2, 3]
  

3. _.concat

Creates a new array concatenating array with any additional arrays and/or values.

  
  var array = [1];
  var other = _.concat(array, 2, [3], [[4]]);
  console.log(other);
  // => [1, 2, 3, [4]]
  console.log(array);
  // => [1]
  

4. _.difference

Creates an array of array values not included in the other given arrays. The order and references of result values are determined by the first array.

  
  _.difference([3, 2, 1], [4, 2]);
  // => [3, 1]
  

5. _.findIndex

This method is like _.find except that it returns the index of the first element predicate returns truthy for instead of the element itself.

  
  var users = [
    { 'user': 'barney',  'active': false },
    { 'user': 'fred',    'active': false },
    { 'user': 'pebbles', 'active': true }
  ];
  _.findIndex(users, function(o) { return o.user == 'barney'; });
  // => 0
  

6. _.flatten

Flattens array a single level deep.

  
  _.flatten([1, [2, [3, [4]], 5]]);
  // => [1, 2, [3, [4]], 5]
  

Application Example using lodash

Let’s build a simple application that manipulates a list of users using lodash functions.

  
  const _ = require('lodash');

  let users = [
      { 'user': 'fred',    'age': 48 },
      { 'user': 'barney',  'age': 34 },
      { 'user': 'fred',    'age': 40 },
      { 'user': 'barney',  'age': 36 }
  ];

  // Remove all duplicate user objects based on user names
  users = _.uniqBy(users, 'user');
  console.log(users);
  // => [ { 'user': 'fred', 'age': 48 }, { 'user': 'barney', 'age': 34 } ]

  // Find the index of the first user who is older than 35
  const index = _.findIndex(users, (user) => user.age > 35);
  console.log(index);
  // => 0

  // Chunk the users into groups of 1
  const userChunks = _.chunk(users, 1);
  console.log(userChunks);
  // => [[{ 'user': 'fred', 'age': 48 }], [{ 'user': 'barney', 'age': 34 }]]
  

With lodash, working with data collections is much easier, cleaner, and often more performant. Whether you’re dealing with arrays, objects, or even complex manipulations, lodash is a powerful library to add to your JavaScript toolkit.

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