Voice of a Developer: Save Coding Time With Lodash.js - Part 29

Sumit Jolly
May 19, 2016
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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.

Introduction

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:

Arrays, objects & strings
Testing values
Creating composite functions

This library is released with MIT license Download.

Note: I am going to refer 4.12 of this library.

Use cases

I will demonstrate benefit of using Lodash.js to simply common problems. It also enhance developer experience to understand and read code better.

Case 1: Sort an array and get unique values.

Naive method

varary = [2, 4, 2, 5, 4, 7];
varsortAry = ary.sort(); // [2, 2, 4, 4, 5, 7]
//run two loops to traverse and match each element, e.g., 2 ===2; 2===4
for (vari = 0; i < sortAry.length; i++)
{
for (var j = i + 1; j < sortAry.length; j++)
{
if (sortAry[i] === sortAry[j]) //equal value and same type operator
{
deletesortAry[i]; //delete element and place 'undefined'
}
}
}
console.log(sortAry); // [undefined × 1, 2, undefined × 1, 4, 5, 7]
//Now we can remove undefined via using filter function
varfinalAry = sortAry.filter(function(v)
{
return v != undefined
})
console.log(finalAry); // [2, 4, 5, 7]

Using Loadash.js

varary = [2,4,2,5,4,7];
varsortAry = ary.sort();
console.log(_.uniq(sortAry)); // [2, 4, 5, 7]
Outcome: reduced lot much code by using _.uniq function of Loadash.js

Case 2: Find a user who based on criteria,

Naive method

var users = [
{
'user': 'Peter',
'age': 36,
'isMember': true
},
{
'user': 'Chris',
'age': 40,
'isMember': false
},
{
'user': 'Alan',
'age': 20,
'isMember': true
}];
for (vari in users)
{
if (users[i].age > 38)
{
var user = users[i];
break;
}
}
console.log(user); // Object {user: "Chris", age: 40, active: false}

Using Loadash.js

var users = [
{
'user': 'Peter',
'age': 36,
'isMember': true
},
{
'user': 'Chris',
'age': 40,
'isMember': false
},
{
'user': 'Alan',
'age': 20,
'isMember': true
}];
_.find(users, function(o)
{
return o.age > 38;
}); //// Object {user: "Chris", age: 40, active: false}
Outcome: reduced lot much code by using _.find
function of Loadash.js

Case 3: Loop over collection.

Naive method

for(vari=0;i<users.length;i++){
console.log(users[i]);
}

Loadash.js

_.times(users.length, function(index){
console.log(users[index]);
});
Outcome:readability is better with loadash.js

Case 4: Truncate a string.

I never wrote a code using Naïve method sojumping directly on Lodash.js implementation. This truncate feature is useful when you are dealing with large text of data and want to truncate it.

Loadash.js

varstr="hello world"; // below will truncate string accordingly
_.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 awesome function to help with.

var fruits =['apple','orange','banana','pomegranate'];
_.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.

var fruits =['apple','orange','banana','pomegranate'];
_.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 Map function.