Building awesome CLIs with JavaScript and Oclif

Building awesome CLIs with JavaScript and Oclif

<strong>Originally published by </strong>Federico Kauffman <em>at&nbsp;</em><a href="" target="_blank"></a>

Originally published by Federico Kauffman at

Let's first define a CLI

A quick Google search yields, of course, a Wikipedia article with the CLI definition:

A command-line interface or command language interpreter (CLI), also known as command-line user interface, console user interface and character user interface (CUI), is a means of interacting with a computer program where the user (or client) issues commands to the program in the form of successive lines of text (command lines). A program which handles the interface is called a command language interpreter or shell (computing).

So, in a nutshell, a CLI is a program that can understand requests made by a user in the form of text and then act and execute code in response to that.

This kind of programs are very useful for many different use cases, from simple CLIs like the cal Bash tool that displays the current month, to extremely complex ones like kubectl for managing Kubernetes clusters.

Even if you don't use CLIs directly every day (which is very unlikely), you probably are being indirectly affected by them, for example, git is a CLI, gcc the GNU compiler, create-react-app a scaffolding CLI for generating React apps, and many more.

How to build your own CLIs

Like many things in the tech world the answer is: "it depends". There are many ways to build them and all of them are probably valid in different contexts. In this case, I am going to explore how to build one with JavaScript and Oclif: a Node.JS Open CLI Framework (by Heroku), which includes a CLI for building CLIs 🤔.


From now on I will assume you are comfortable with JavaScript and the NPM ecosystem in general, if you are not, you will probably get a general idea, but I recommend you read something about that before starting 😃.

Getting started with Oclif

In my opinion, building something is usually a great way to learn, so in this case, I did some brainstorming with @flarraa and decided to build a "Copa Libertadores" CLI (see Wikipedia) .

The idea is to provide a set of commands that can retrieve and display information about the already played matches and upcoming ones for the "Copa Libertadores" championship.

Let's dig in!

The Oclif CLI, has two possible ways to generate CLI projects, one is npx oclif single mynewcli and the second one is npx oclif multi mynewcli, in this case, we are going to generate a multi-command CLI.

We would like our command to look like libertadores games:alllibertadores games:pastlibertadores games:upcoming and this is consistent with Oclif's multi-command CLI generation.

Initializing the project

First, we initialize the project by doing:

npx oclif multi libertadores-cli

This will ask some questions and after that, it will install everything you need to start coding!

$ npx oclif multi libertadores
npx: installed 442 in 32.454s
 _-----_     ╭──────────────────────────╮
|       |    │      Time to build a     │
|--(o)--|    │  multi-command CLI with  │

---------´ │ oclif! Version: 1.13.1 │ ( _´U_ ) ╰──────────────────────────╯
/A\ /
| ~ |
´ |° ´ Y

? npm package name libertadores-cli
? command bin name the CLI will export libertadores
? description A simple CLI to get information about "Copa Libertadores" right in your terminal
? author Federico Kauffman
? version 0.0.0
? license MIT
? Who is the GitHub owner of repository ( streaver
? What is the GitHub name of repository ( libertadores-cli
? Select a package manager yarn
? TypeScript No
? Use eslint (linter for JavaScript) Yes
? Use mocha (testing framework) Yes
? Add CI service config circleci (continuous integration/delivery service)

I have selected some defaults I like and now you have a bunch of files and folders which will be our main structure for the project. Next enter the directory with cd libertadores-cli.

I am going to briefly explain what Oclif has generated for us:

├── bin
│ ├── run
│ └── run.cmd
├── package.json
├── src
│ ├── commands
│ │ └── hello.js
│ └── index.js
├── test
│ ├── commands
│ │ └── hello.test.js
│ └── mocha.opts
└── yarn.lock

5 directories, 9 files

Looking at the tree of files you can see the bin directory which contains the binaries to run the command on each platform (Unix/Windows).

You see the src folder with an index.js file which simply exports an internal Oclif package which will load the available commands, and those commands are defined in the files placed in the src/commands folder. By default, Oclif generates a hello command, let's run that and see what we have:

$ ./bin/run

A simple CLI to get information about "Copa Libertadores" right in your terminal

libertadores-cli/0.0.0 darwin-x64 node-v11.13.0

$ libertadores [COMMAND]

hello Describe the command here
help display help for libertadores

If you run the hello sub-command you get:

$ ./bin/run hello

hello world from ./src/commands/hello.js

Last but not least, you have the tests folder where you will place all your tests, in fact, Oclif already created some tests, and we can run them with npm run test or yarn test.

Creating the first command

First, we can delete the hello command since we are not going to use it, simply delete the src/command/hello.js and tests/commands/hello.test.js.

Now we can use the Oclif CLI generator command, let's create the games:all command with:

npx oclif command games:all

This will create all the files needed for the command (including tests) and also will update the file automatically to include the new command.

We are going to get the details for "Copa Libertadores" from, and we are going to use puppeteer to enter the site and get the data.

$ yarn add puppeteer --save
const puppeteer = require("puppeteer");
class AllCommand extends Command {
async run() {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto(
{ waitUntil: "load", timeout: 0 }

// Insert some really crazy code to parse the HTML
// you can find this at



Now we can execute libertadores games:all and we will get the results right there on the terminal:

As you may have noticed I also added a "loading" feature to give the user some visual feedback. In order to add that, you simply install the package cli-ux and then wrap the "slow" parts of the code in some start/stop calls:

Install it like this:

yarn add cli-ux --save

Add the spinner with something like:

const { cli } = require('cli-ux');

cli.action.start('Fetching data');
//Do something that takes time

Now, at this point we have the CLI, we can write tests for it! Oclif comes with some nice defaults for testing this kind of CLIs. In this particular case, you just want to test that the output to the terminal is what you expect. Fortunately, that is exactly what the auto-generated test for the command does, you only need to adapt that code!

I will leave this task to you (the reader, just like Math books) 🙄...or you can check them out in the official repository for the "Copa Libertadores" CLI.

Install the CLI, stay up-to-date and don't miss games anymore ❤️⚽️!


Thanks for reading :heart: If you liked this post, share it with all of your programming buddies! Follow me on Facebook | Twitter

Learn More

☞ Talking to Python from JavaScript (and Back Again!)

☞ Top 12 Javascript Tricks for Beginners

☞ Functional Programming in JavaScript

☞ JavaScript for Machine Learning using TensorFlow.js

☞ Learn JavaScript - JavaScript Course for Beginners

☞ The Complete JavaScript Course 2019: Build Real Projects!

☞ Become a JavaScript developer - Learn (React, Node,Angular)

☞ JavaScript: Understanding the Weird Parts

☞ Vue JS 2 - The Complete Guide (incl. Vue Router & Vuex)

☞ The Full JavaScript & ES6 Tutorial - (including ES7 & React)

☞ JavaScript - Step By Step Guide For Beginners

☞ The Web Developer Bootcamp

☞ MERN Stack Front To Back: Full Stack React, Redux & Node.js

JavaScript Tutorial: if-else Statement in JavaScript

JavaScript Tutorial: if-else Statement in JavaScript

This JavaScript tutorial is a step by step guide on JavaScript If Else Statements. Learn how to use If Else in javascript and also JavaScript If Else Statements. if-else Statement in JavaScript. JavaScript's conditional statements: if; if-else; nested-if; if-else-if. These statements allow you to control the flow of your program's execution based upon conditions known only during run time.

Decision Making in programming is similar to decision making in real life. In programming also we face some situations where we want a certain block of code to be executed when some condition is fulfilled.
A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

JavaScript’s conditional statements:

  • if
  • if-else
  • nested-if
  • if-else-if

These statements allow you to control the flow of your program’s execution based upon conditions known only during run time.

  • if: if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
   // Statements to execute if
   // condition is true

Here, condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it.
If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,


// Here if the condition is true, if block 
// will consider only statement1 to be inside 
// its block.

Flow chart:


<script type = "text/javaScript"> 

// JavaScript program to illustrate If statement 

var i = 10; 

if (i > 15) 
document.write("10 is less than 15"); 

// This statement will be executed 
// as if considers one statement by default 
document.write("I am Not in if"); 

< /script> 


I am Not in if
  • if-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.
if (condition)
    // Executes this block if
    // condition is true
    // Executes this block if
    // condition is false


<script type = "text/javaScript"> 

// JavaScript program to illustrate If-else statement 

var i = 10; 

if (i < 15) 
document.write("10 is less than 15"); 
document.write("I am Not in if"); 

< /script> 


i is smaller than 15
  • nested-if A nested if is an if statement that is the target of another if or else. Nested if statements means an if statement inside an if statement. Yes, JavaScript allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
if (condition1) 
   // Executes when condition1 is true
   if (condition2) 
      // Executes when condition2 is true


<script type = "text/javaScript"> 

// JavaScript program to illustrate nested-if statement 

var i = 10; 

if (i == 10) { 

// First if statement 
if (i < 15) 
	document.write("i is smaller than 15"); 

// Nested - if statement 
// Will only be executed if statement above 
// it is true 
if (i < 12) 
	document.write("i is smaller than 12 too"); 
	document.write("i is greater than 15"); 
< /script> 


i is smaller than 15
i is smaller than 12 too
  • if-else-if ladder Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
if (condition)
else if (condition)


<script type = "text/javaScript"> 
// JavaScript program to illustrate nested-if statement 

var i = 20; 

if (i == 10) 
document.wrte("i is 10"); 
else if (i == 15) 
document.wrte("i is 15"); 
else if (i == 20) 
document.wrte("i is 20"); 
document.wrte("i is not present"); 
< /script> 


i is 20

How to Retrieve full Profile of LinkedIn User using Javascript

How to Retrieve full Profile of LinkedIn User using Javascript

I am trying to retrieve the full profile (especially job history and educational qualifications) of a linkedin user via the Javascript (Fetch LinkedIn Data Using JavaScript)

Here we are fetching LinkedIn data like Username, Email and other fields using JavaScript SDK.

Here we have 2 workarounds.

  1. Configuration of linkedIn developer api
  2. Javascript Code to fetch records

Configuration of linkedIn developer api

In order to fetch records, first we need to create developer api in linkedin which will act as token/identity while fetching data from other linkedin accounts.

So to create api, navigate to and click on 'Create Application'.

After navigating, fill in details like name, description and other required fields and then submit.

As we submit, it will create Client ID and Client Secret shown below, which we will be using in our code while communicating to fetch records from other LinkedIn account.

Note: We need to provide localhost Url here under Oauth 2.0. I am using my localhost, but you can probably use other production URLs under Oauth 2.0 where your app is configured. It will make your api  consider the Url as trusted which fetching records.

Javascript Code to fetch records

For getting user details like first name, last name,User image can be written as,

<script type="text/javascript" src="">  
    api_key: XXXXXXX //Client ID  
    onLoad: OnLinkedInFrameworkLoad //Method that will be called on page load  
    authorize: true  
<script type="text/javascript">  
    function OnLinkedInFrameworkLoad() {  
        IN.Event.on(IN, "auth", OnLinkedInAuth);  
    function OnLinkedInAuth() {  
    function ShowProfileData(profiles) {  
        var member = profiles.values[0];  
        var id =;  
        var firstName = member.firstName;  
        var lastName = member.lastName;  
        var photo = member.pictureUrl;  
        var headline = member.headline;  
        //use information captured above  
        var stringToBind = "<p>First Name: " + firstName + " <p/><p> Last Name: " + lastName + "<p/><p>User ID: " + id + " and Head Line Provided: " + headline + "<p/>"  
        document.getElementById('profiles').innerHTML = stringToBind;  

Kindly note we need to include '' as src under script type as it will act on this Javascript SDK provided by Linkedin.

In the same way we can also fetch records of any organization with the companyid as keyword.

    <script type="text/javascript" src="">  
        api_key: XXXXXXX ////Client ID  
        onLoad: onLinkedInLoad  
        authorize: true  
    <div id="displayUpdates"></div>  
    <script type="text/javascript">  
        function onLinkedInLoad() {  
            IN.Event.on(IN, "auth", onLinkedInAuth);  
            console.log("On auth");  
        function onLinkedInAuth() {  
            var cpnyID = XXXXX; //the Company ID for which we want updates  
            IN.API.Raw("/companies/" + cpnyID + "/updates?event-type=status-update&start=0&count=10&format=json").result(displayCompanyUpdates);  
            console.log("After auth");  
        function displayCompanyUpdates(result) {  
            var div = document.getElementById("displayUpdates");  
            var el = "<ul>";  
            var resValues = result.values;  
            for (var i in resValues) {  
                var share = resValues[i].updateContent.companyStatusUpdate.share;  
                var isContent = share.content;  
                var isTitled = isContent,  
                    isLinked = isContent,  
                    isDescription = isContent,  
                    isThumbnail = isContent,  
                    isComment = isContent;  
                if (isTitled) {  
                    var title = isContent.title;  
                } else {  
                    var title = "News headline";  
                var comment = share.comment;  
                if (isLinked) {  
                    var link = isContent.shortenedUrl;  
                } else {  
                    var link = "#";  
                if (isDescription) {  
                    var description = isContent.description;  
                } else {  
                    var description = "No description";  
                if (isThumbnailz) { 
                var thumbnailUrl = isContent.thumbnailUrl; 
                } else { 
                var thumbnailUrl = ""; 
                if (share) {  
                    var content = "<a target='_blank' href=" + link + ">" + comment + "</a><br>";  
                    //el += "<li><img src='" + thumbnailUrl + "' alt=''>" + content + "</li>";  
                    el += "<li><div>" + content + "</div></li>";  
            el += "</ul>";  
            document.getElementById("displayUpdates").innerHTML = el;  

We can get multiple metadata while fetching records for any any organization. We can get company updates as shown below.


We can also fetch any company specific data like company job updates/post, total likes, comments, and number of views along with a lot of metadata we can fetch which I have shown below.

Thank you for reading !

7 Best Javascript Iframe Libraries

7 Best Javascript Iframe Libraries

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

1. Zoid

A cross-domain component toolkit, supporting:

  • Render an iframe or popup on a different domain, and pass down props, including objects and functions
  • Call callbacks natively from the child window without worrying about post-messaging or cross-domain restrictions
  • Create and expose components to share functionality from your site to others!
  • Render your component directly as a React, Vue or Angular component!
    It's 'data-down, actions up' style components, but 100% cross-domain using iframes and popups!


2. Postmate

Postmate is a promise-based API built on postMessage. It allows a parent page to speak with a child iFrame across origins with minimal effort.


3. Iframe Resizer

Keep same and cross domain iFrames sized to their content with support for window/content resizing, in page links, nesting and multiple iFrames



4. Iframely

Embed proxy. Supports over 1800 domains via custom parsers, oEmbed, Twitter Cards and Open Graph



5. React Frame component

This component allows you to encapsulate your entire React application or per component in an iFrame.



6. Seamless.js

A seamless iframe makes it so that visitors are unable to distinguish between content within the iframe and content beside the iframe. Seamless.js is a JavaScript library (with no dependencies) that makes working with iframes easy by doing all the seamless stuff for you automatically.



7. Porthole

A proxy to safely communicate to cross-domain iframes in javascript



Thank for read!