Introduction

JavaScript is a language of Web. This series of articles will talk about my observations learned during my decade of software development experience with JavaScript.
Before moving further let us look at the previous articles of the JavaScript series:
In this article, we will explore functional programming aspects of JavaScript using a popular library called Loadash.js. It makes JavaScript easier. I use Lodash.js as Swiss Army knife to help me in breaking complex problems into smaller chunks and faster delivery.

JavaScript

In day-to-day programming, we work on solving business problems and working with arrays, numbers, objects, strings, etc. Loadash.js works great with these:
This library is released with MIT license Download.
Note: I am going to refer to 4.12 of this library.
Use cases
I will demonstrate benefit of using Lodash.js to simply common problems. It also enhance the developer experience to understand and read code better.
Case 1: Sort an array and get unique values.
Naive method
  1. varary = [2, 4, 2, 5, 4, 7];
  2. varsortAry = ary.sort(); // [2, 2, 4, 4, 5, 7]
  3. //run two loops to traverse and match each element, e.g., 2 ===2; 2===4
  4. for (vari = 0; i < sortAry.length; i++)
  5. {
  6. for (var j = i + 1; j < sortAry.length; j++)
  7. {
  8. if (sortAry[i] === sortAry[j]) //equal value and same type operator
  9. {
  10. deletesortAry[i]; //delete element and place 'undefined'
  11. }
  12. }
  13. }
  14. console.log(sortAry); // [undefined × 1, 2, undefined × 1, 4, 5, 7]
  15. //Now we can remove undefined via using filter function
  16. varfinalAry = sortAry.filter(function(v)
  17. {
  18. return v != undefined
  19. })
  20. console.log(finalAry); // [2, 4, 5, 7]
Using Loadash.js
  1. varary = [2,4,2,5,4,7];
  2. varsortAry = ary.sort();
  3. console.log(_.uniq(sortAry)); // [2, 4, 5, 7]
  4. Outcome: reduced lot much code by using _.uniq function of Loadash.js
Case 2: Find a user who based on criteria,
Naive method
  1. var users = [
  2. {
  3. 'user': 'Peter',
  4. 'age': 36,
  5. 'isMember': true
  6. },
  7. {
  8. 'user': 'Chris',
  9. 'age': 40,
  10. 'isMember': false
  11. },
  12. {
  13. 'user': 'Alan',
  14. 'age': 20,
  15. 'isMember': true
  16. }];
  17. for (vari in users)
  18. {
  19. if (users[i].age > 38)
  20. {
  21. var user = users[i];
  22. break;
  23. }
  24. }
  25. console.log(user); // Object {user: "Chris", age: 40, active: false}
Using Loadash.js
  1. var users = [
  2. {
  3. 'user': 'Peter',
  4. 'age': 36,
  5. 'isMember': true
  6. },
  7. {
  8. 'user': 'Chris',
  9. 'age': 40,
  10. 'isMember': false
  11. },
  12. {
  13. 'user': 'Alan',
  14. 'age': 20,
  15. 'isMember': true
  16. }];
  17. _.find(users, function(o)
  18. {
  19. return o.age > 38;
  20. }); //// Object {user: "Chris", age: 40, active: false}
  21. Outcome: reduced lot much code by using _.find
  22. function of Loadash.js
Case 3: Loop over collection.
Naive method
  1. for(vari=0;i<users.length;i++){
  2. console.log(users[i]);
  3. }
Loadash.js
  1. _.times(users.length, function(index){
  2. console.log(users[index]);
  3. });
  4. Outcome:readability is better with loadash.js
Case 4: Truncate a string.
I never wrote code using Naïve method so jumping directly on Lodash.js implementation. This truncate feature is useful when you are dealing with the large text of data and want to truncate it.
Loadash.js
  1. varstr="hello world"; // below will truncate string accordingly
  2. _.truncate(str, {'length':7}); // hell…
Case 5: Shuffle a response.
If you have noticed in online assessments questions are shuffled for each candidate. Lodash.js offers the awesome function to help with.
  1. var fruits =['apple','orange','banana','pomegranate'];
  2. _.shuffle(fruits); // ["orange", "apple", "pomegranate", "banana"]
Note: The output of _.shuffle could vary because it uses a random permutation Fisher-Yates algorithm.
Case 6: Gets a random selection.
  1. var fruits =['apple','orange','banana','pomegranate'];
  2. _.sample(fruits); // pomegranate; this output could vary
Case 7: Map and Reduce functions.
If you remember we explored map and reduce functions in Array methods in article 17.
Loadsh.js provides a convenient approach for both these functions, e.g., get names from users collection and we will use the Map function.
  1. _.map(users, 'user'); // ["Peter", "Chris", "Alan"]
  2. //To change all users name into UpperCase
  3. _.map(users, function(u){varobj=u.user; return obj.toUpperCase();});
  4. //["PETER", "CHRIS", "ALAN"]
Reduce function has similar arguments but it applies to reduce approach to get a single value. Example - we want to sum number greater than 20.
  1. _.reduce([10, 15, 20, 35, 30, 45], function (accumulator, value) {
  2. if (value > 20)
  3. return accumulator + value;
  4. else
  5. return 0;
  6. }); // sum is 110
Case 8: String template is very common for the substitution of data.
Naïve method
  1. var name='Andriana';
  2. var interest='Programming';
  3. varstr="Hello, "+name+". Your interest is "+interest;
  4. console.log(str); // Hello, Andriana. Your interest is Programming
Loadash.js
  1. vartpl = _.template('Hello, <%= name %>. Your interest is <%= interest%>');
  2. tpl({
  3. name: 'Andriana', interest: 'Programming'});
  4. console.log(tpl);//Hello, Andriana. Your interest is Programming

Summary

I am an ardent fan of Lodash.js and developers must try to solve problems quickly. Please share your feedback/comments.