Alex Arriaga

alex-arriaga February 20, 2018

How to Install Node.js on CentOS 7

Enterprise Development, GNU/Linux, Node.js No Reply

The Problem

Today, I was testing the new Angular 4 Scripting Application sample provided by IBM as a starting point for creating Script Portlet based Apps. However, my development environment is a CentOS 7 computer, and I usually don’t work with Node.js in that computer, so here the simple steps to install Node.js in a CentOS 7 machine, let’s proceed:

The Solution

Since CentOS 7 uses RPM as the package manager by default (CentOS is basically the open version of Red Hat Enterprise Linux or RHEL), the easiest way to install Node.js is following the instructions in the official Node.js documentation.

Step 1. Download the installation binaries of the Node.js version you are interested in, in my case I wanted to have the latest stable version or long term support (LTS) which is version 8.x:

curl --silent --location https://rpm.nodesource.com/setup_8.x | sudo bash -

1	curl --silent --location https://rpm.nodesource.com/setup_8.x \| sudo bash -

Step 2. Proceed to install

sudo yum install -y nodejs

1	sudo yum install -y nodejs

Step 3. Check the installation was successful

node --version

# You will see something like
v.8.9.4

node --version

# You will see something like

v.8.9.4

If previous command gives you the Node.js version, you are all set. You also have npm so you can continue building awesome apps.

That’s it!

Hope you find this information useful, see you next time and remember be happy with your code.

alex-arriaga February 15, 2018

Enable CORS in a Node.js Application

Enterprise Development, Node.js No Reply

The Problem

So… you are creating an awesome Single Page Application with your favorite front-end framework (Vue.js, Angular, etc…) you need to connect your app with an external service; you have selected a JavaScript library to make the AJAX calls (like Axios), everything seem to be perfect, you create your method to get the remote data with something like this:

var serverURL = 'http://example.com:3000/my-rest-api-end-point-to-get-data';
var _this = this;
var configAxios = {
    url: serverURL,
    method: 'get',
    responseType: 'json',
    data: {},
    headers: {}
};

// Getting information using Axios library
axios.request(configAxios).then(function(response) {
    console.log(response);
    _this.myData = response.data;
});

var serverURL = 'http://example.com:3000/my-rest-api-end-point-to-get-data';

var _this = this;

var configAxios = {

url: serverURL,

method: 'get',

responseType: 'json',

data: {},

headers: {}

};

// Getting information using Axios library

axios.request(configAxios).then(function(response) {

console.log(response);

_this.myData = response.data;

});

And suddenly, your app is broken, why? If you go to the console, you will see an error similar to this one:

No ‘Access-Control-Allow-Origin’ header is present on the requested resource. Origin ‘null’ is therefore not allowed access. The response had HTTP status code 401.

The Solution

Because of security, you cannot request resources that are not in your domain (same server, same port). The solution is quite simple:

You need to authorize the origins that can make this type of calls.

This authorization is known as enabling CORS, this operation needs to be done in your SERVER. Here is an example using an Express.js application, see step 3 in the comments:

const express = require('express');
const app = express();
const path = require('path');
const server = require('http').createServer(app);

const morgan = require('morgan');
const bodyParser = require('body-parser');

const port = process.env.PORT || 3300;

const pollsRouter = require('./api/routers/polls-router');
const pollsService = require('./api/services/polls-dummy.service');

// 1. Morgan middleware for logging
app.use(morgan('dev'));

// 2. Express static index.html file
app.get('/', (req, res) => {
    res.sendFile(path.join(__dirname, 'index.html'));
});

// 3. Enable CORS on ExpressJS to avoid cross-origin errors when calling this server using AJAX
// We are authorizing all domains to be able to manage information via AJAX (this is just for development)

app.use(function(req, res, next) {
    // Instead of "*" you should enable only specific origins
    res.header('Access-Control-Allow-Origin', '*');
    // Supported HTTP verbs
    res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
    // Other custom headers
    res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
    next();
});

// 4. Body parser middleware to auto-parse request body to JSON
app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());


// 5. Run the server
server.listen(port, () => {
    console.log('Server active on port: %d', port);
});

const express = require('express');

const app = express();

const path = require('path');

const server = require('http').createServer(app);

const morgan = require('morgan');

const bodyParser = require('body-parser');

const port = process.env.PORT || 3300;

const pollsRouter = require('./api/routers/polls-router');

const pollsService = require('./api/services/polls-dummy.service');

// 1. Morgan middleware for logging

app.use(morgan('dev'));

// 2. Express static index.html file

app.get('/', (req, res) => {

res.sendFile(path.join(__dirname, 'index.html'));

});

// 3. Enable CORS on ExpressJS to avoid cross-origin errors when calling this server using AJAX

// We are authorizing all domains to be able to manage information via AJAX (this is just for development)

app.use(function(req, res, next) {

// Instead of "*" you should enable only specific origins

res.header('Access-Control-Allow-Origin', '*');

// Supported HTTP verbs

res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');

// Other custom headers

res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');

next();

});

// 4. Body parser middleware to auto-parse request body to JSON

app.use(bodyParser.urlencoded({ extended: true }));

app.use(bodyParser.json());

// 5. Run the server

server.listen(port, () => {

console.log('Server active on port: %d', port);

});

Simple and fast, I hope you find this useful for your implementations.

See you next time!

alex-arriaga February 15, 2018

How to set moment.js timezone when creating a date

JavaScript, Web Development No Reply

The Problem

Since Moment.js is a library that runs client-side, when you create a new date using it; the constructor will take the current user’s timezone. This is not convenient when you want to display a list of dates that don’t depend on the user’s browser.

Let’s see an example of this, imagine you have an URL with an event that will start on Feb 15th, 2018 at 7 PM in the GTM-6 timezone, following table will be correct ONLY if you are in the GMT-6 timezone! because it represents hours in several timezones around the world taking that timezone as the relative time. This can be confusing for an user in Spain or for a visitor from New York.

Zone	Time
America/Mexico_City	7pm CST
America/Bogota	8pm -05
America/Caracas	9pm -04
America/Lima	8pm -05
America/Guayaquil	8pm -05
America/Santiago	10pm -03
America/El_Salvador	7pm CST
America/Argentina/Buenos_Aires	10pm -03
Europe/Madrid	2am CET
America/Los_Angeles	5pm PST
America/Denver	6pm MST
America/New_York	8pm EST

Solution

Fortunately, Moment.js provides an out-of-the-box feature that allows to set the timezone we want to use when creating our original date, let’s see following code as an example:

var startDateAndTimeString = '2018-02-15 19:00:00';

// We set the timezone as a second parameter
var startDateAndTime = moment(startDateAndTimeString).tz('America/Mexico_City');

// Now, you could format your date to be displayed in different timezones
function formatDateToAnotherTimezone(anotherTimezone, startDateAndTime) {
 return moment(startDateAndTime).tz(anotherTimezone).format('ha z');
}

// This will get: 2am CET
var startDateAndTimeForMadridSpain =formatDateToAnotherTimezone('Europe/Madrid',startDateAndTime);

var startDateAndTimeString = '2018-02-15 19:00:00';

// We set the timezone as a second parameter

var startDateAndTime = moment(startDateAndTimeString).tz('America/Mexico_City');

// Now, you could format your date to be displayed in different timezones

function formatDateToAnotherTimezone(anotherTimezone, startDateAndTime) {

return moment(startDateAndTime).tz(anotherTimezone).format('ha z');

}

// This will get: 2am CET

var startDateAndTimeForMadridSpain =formatDateToAnotherTimezone('Europe/Madrid',startDateAndTime);

For this to work, please be sure you have loaded the Moment Timezone plugin.

That’s it! Awesome, isn’t it?

See you next time…

alex-arriaga February 15, 2018

Wherever you are, please act as a Professional Senior

Business, Career Development, Enterprise Development No Reply

Disclaimer: this is my personal opinion, this is just my perspective, that doesn’t mean I have the answers or what I am about to say is the rule.

In the Web Development and IT companies world, we are always looking for talented people to join our lines; however, it is always difficult to find professionals that not only have great technical skills but soft skills as well.

Last week, I was asked to provide a description about which characteristics a senior engineer/consultant should have to be considered as that, here is my personal opinion about what I think a professional senior should bring to the table:

Be on time

Web Development and Enterprise Consulting is Exciting but Hard

This is not the university, where you could arrive late, where you could decide not to do your homework, where you can think you are good and nothing else can be added to your project just to pass the semester.

In the enterprise consulting activity, we must be on time (or if not, we have to explain why that occurred), we have to understand someone is investing in us, is trusting us to help them.

Be patient

But have your plan B ready, in case you don’t get what you expect

All of us have things to do and accomplish, you are not the only person who depends on the other’s decision. Wait, be patient, be tolerant. In the enterprise world, people are really busy, the decision will take some time.

However, try to always have a plan B in case the decisions that are blocking you are not being made or taking more time. Try to be in the other person’s shoes:

What my client would like to have?
How can I make his life easier?
Can I take a partial decision with the information I have at this moment?
Can I take a measured risk to continue my work?
May I propose something to accelerate the decision-making process?

Be prepared to travel

Being a senior professional is also understanding your company will need you

You will be asked to sacrifice your time in order to deliver what is needed. In the enterprise world, being able to travel and live for a medium/long term in another city is almost a must.

You will probably have to leave your family for a while. If you disagree with this, it is fine, being far away from our family or the things we are used to is hard, but if you take the challenge, do your best to end the project on time and help your team to succeed.

If not, please talk to the right people, please, don’t be silent; they need to know you are not comfortable with the project/tasks you are being asked to deliver.

Be ready to learn

Our area is a fast-evolving zone, nothing is static, everything is being constantly improved

Even if you are not using specific tools, methodologies or processes in the present, that doesn’t mean you should ignore them completely. Our area of knowledge is moving faster and faster, which was valid one year ago, it may be not the best option today.

There is a revolution in knowledge happening as we speak, exciting areas are coming to the enterprise world: Artificial Intelligence, Deep Machine Learning, Neural Networks, Block-chain stuff, Linked Data, Data Science, Virtual Reality…

Be aware of hierarchies

They exist, you cannot remove them, but you can play nicely with them

If you are a young person, it is probably you don’t love hierarchies. The people from your generation consider hierarchies should not exist, you usually respect the people based on what they have demonstrated to you (knowledge, more likely).

In the enterprise world hierarchies exist, there are people with a huge ego, people that have not understood generations are changing… your challenge is to provide them a wider vision, help them to see how your generation envision the world. Don’t see them as the enemy to defeat but as an ally than can help you build the company and the world you envision.

We cannot expect they accept our points right away! They have the experience, they have lived in a different time, they learned to provide solutions, make businesses, keep companies alive with a different approach.

Be an active listener

Stay alert, listen your team and go to the action even if it wasn’t requested

One of the most difficult skills to master is to listen without criticize; everyone has an opinion, all of us have different perspectives about what we believe is right or wrong.

The reality is no one has the final or the ultimate answer

Being an active listener doesn’t mean you have to be silent all the time, on the contrary, you should speak aloud when no one is hearing you; just be sure you have the points and the foundations to discuss and try to communicate why your proposal or you way to see the problems is better at that moment.

What do you think about this? Please let me know your opinion, I will be glad to hear you.

Best regards.

alex-arriaga February 15, 2018

How to use the Plugin Otherwise in IBM WCM 8 and 9

Enterprise Development, IBM Web Content Manager No Reply

The challenge

Imagine you want to run a kind of conditional if with a fallback (else) for example: you would like to have some custom HTML markup when there is no description set on a piece of content. Let’s see following pseudocode:

IF is_There_A_Description(current_Content)
    DISPLAY description
ELSE
    DISPLAY a default text

IF is_There_A_Description(current_Content)

DISPLAY description

ELSE

DISPLAY a default text

So, how could we emulate this behaviour on IBM WCM? Simple…

The solution

Let’s use a server-side solution using the NotEquals plugin, which is really easy to apply, let’s see an example:

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']"]
	<div class="b-content__description">
               [Property context='current' type='content' field='description']
	</div>
[/Plugin:NotEquals]
[Plugin:Otherwise]<!-- This is our "else" -->
<!-- No description was set, do some custom logic here -->
[/Plugin:Otherwise]

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']"]

[Property context='current' type='content' field='description']

</div>

[/Plugin:NotEquals]

[Plugin:Otherwise]

[/Plugin:Otherwise]

Explanation

The plugin NotEquals requires two mandatory parameters: text1 and text2 (both strings). In this example, we have text1=”” compared with text2=”[Property context=”current” type=”content” field=”description”].

When WCM renders this HTML with the [Property] meta-tag, it will compare the text2 with text1 and if text2 is not empty, the HTML inside the NotEquals plugin will be rendered, otherwise (else) no HTML will be generated. Simple and elegant.

However… be careful when combining / nesting conditionals:

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']"]
    [Plugin:NotEquals text1="generic-description" text2="[Property context='current' type='content' field='description']"]
	<div class="b-content__description">
               [Property context='current' type='content' field='description']
	</div>
    [/Plugin:NotEquals]
[/Plugin:NotEquals]
[Plugin:Otherwise]<!-- This is our "else" -->
<!-- No description was set, do some custom logic here -->
[/Plugin:Otherwise]

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']"]

[Plugin:NotEquals text1="generic-description" text2="[Property context='current' type='content' field='description']"]

[Property context='current' type='content' field='description']

</div>

[/Plugin:NotEquals]

[Plugin:Otherwise]

[/Plugin:Otherwise]

Previous conditional will not work, since the Otherwise plugin is not going to know under which context should act.

IBM provides a way to solve this using what is is called scope. Let’s change a bit our code to set this scope parameter in BOTH NotEquals and Otherwise plugins.

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']" scope="1"]
    [Plugin:NotEquals text1="generic-description" text2="[Property context='current' type='content' field='description']" scope="2"]
	<div class="b-content__description">
               [Property context='current' type='content' field='description']
	</div>
    [/Plugin:NotEquals]
[/Plugin:NotEquals]
[Plugin:Otherwise scope="1"]<!-- This is our "else" with scope="1" which means, it will act with the first NotEquals plugin -->
<!-- No description was set, do some custom logic here -->
[/Plugin:Otherwise]

[Plugin:NotEquals text1="" text2="[Property context='current' type='content' field='description']" scope="1"]

[Plugin:NotEquals text1="generic-description" text2="[Property context='current' type='content' field='description']" scope="2"]

[Property context='current' type='content' field='description']

</div>

[/Plugin:NotEquals]

[Plugin:Otherwise scope="1"]

[/Plugin:Otherwise]

Otherwise plugin restrictions

The Otherwise plugin ONLY works with:

Equals plug-in
NotEquals plug-in
Matches plug-in

I hope you find this information useful, and remember, be happy with your code!

alex-arriaga March 12, 2017

Installing a Node.js App as a regular GNU/Linux process

GNU/Linux, Node.js, Operating Systems No Reply

While in development of any Node.js application we usually configure a npm start task to run it; but when you are ready to go to production that concept is not useful anymore. Until that moment, we have tested our application using the regular npm process (npm start); but now, we are going to need to go one step further. We will install a process manager for Node.js called PM2: http://pm2.keymetrics.io/.

PM2 will allow us to register our Node.js application as a regular process in GNU/Linux.

1) Install PM2:

sudo npm install pm2 -g

1	sudo npm install pm2 -g

2) Run pm2 start command to run the application:

// This also adds the application to PM2's process list, 
// which is outputted every time you start an application
sudo pm2 start /path/to/main/nodejs/script

// For example:
sudo pm2 start /usr/share/nginx/html/wetraining-chat/server.js

// This also adds the application to PM2's process list,

// which is outputted every time you start an application

sudo pm2 start /path/to/main/nodejs/script

// For example:

sudo pm2 start /usr/share/nginx/html/wetraining-chat/server.js

Figure 1. Example of server process in PM2.

PM2 automatically assigns an Application name and a PM2 id. In this case since the file is “server.js”; the resulting process would be “server”. PM2 also maintains other information, such as the PID of the process, its current status, and memory usage.

Applications running under PM2 will be restarted automatically if the application crashes or is killed, but an additional step needs to be taken to get the application to launch on system startup (boot or reboot). To solve this, PM2 provides the startup subcommand.

The startup subcommand generates and configures a startup script to launch PM2 and its managed processes on server boots. You must also specify the platform you are running on, which is ubuntu, in our case:

sudo pm2 startup ubuntu

1	sudo pm2 startup ubuntu

Useful PM2 commands

// Stop the application
pm2 stop APP_NAME
  
// Restart an application
sudo pm2 restart APP_NAME
  
// List the applications currently managed by PM2
sudo pm2 list
  
// Get meta-data about an application
sudo pm2 info APP_NAME
  
// Display the application status, CPU, and memory usage
sudo pm2 monit

// Stop the application

pm2 stop APP_NAME

// Restart an application

sudo pm2 restart APP_NAME

// List the applications currently managed by PM2

sudo pm2 list

// Get meta-data about an application

sudo pm2 info APP_NAME

// Display the application status, CPU, and memory usage

sudo pm2 monit

I hope you find this information useful. PM2 is an excellent option to register our Node.js app as regular GNU/Linux. There are other options out there like Strong Loop Process Manager and Forever. Have you used one of them? Let me know your opinion.

alex-arriaga September 27, 2016

Learning Functional Programming with JavaScript – JSUnconf 2016

JavaScript, Web Development 2 Replies

Functional Programming? Oh yeah, that is one of the most interesting paradigms in computer sciences that is being used since a long time ago, however in the last years it has obtained a particular interest because of JavaScript, in fact, I bet you are being using functional programming without even know it.

In this great conference by Anjana Vakil you will learn the fundamentals of this paradigm as well as some examples using the JavaScript language.

As a complement to this conference here is an awesome article called “A practical introduction to functional programming by Mary Rose Cook”

alex-arriaga August 18, 2016

Delete files with a pattern recursively using the terminal

GNU/Linux, Mac OSX, Operating Systems No Reply

This is just a simple way to delete files recursively using your terminal in any UNIX-like operating system:

find . -type f -name "FILES_PATTERN" -exec rm {} \;

// Example
find . -type f -name "*.mp3" -exec rm {} \;

find . -type f -name "FILES_PATTERN" -exec rm {} \;

// Example

find . -type f -name "*.mp3" -exec rm {} \;

Explanation

-name “FILES_PATTERN” : File pattern.
-exec rm -rf {} \; : Delete all files that match the file pattern.
-type f : Not include directories.

alex-arriaga August 18, 2016

How to know if a user is authenticated or not in WCM 8 and 8.5

Enterprise Development, IBM Web Content Manager No Reply

This is pretty simple way to check if any user has a session started or not; this is useful in cases where you want to display or execute an specific code depending on the user session. To create this kind of validation we can take advantage of the WCM plugins Equals and NotEquals

[Plugin:Equals text1="true" text2="[Plugin:RequestAttribute key='userLoggedIn' mode='get']"]
<!-- Authenticated block -->
<p class="authenticated">I have a session.</p>
[/Plugin:Equals]

[Plugin:NotEquals text1="true" text2="[Plugin:RequestAttribute key='userLoggedIn' mode='get']"]
<!-- Not authenticated block -->
<p class="anonymous">I DON'T have a session.</p>
[/Plugin:NotEquals]

[Plugin:Equals text1="true" text2="[Plugin:RequestAttribute key='userLoggedIn' mode='get']"]

<p class="authenticated">I have a session.</p>

[/Plugin:Equals]

[Plugin:NotEquals text1="true" text2="[Plugin:RequestAttribute key='userLoggedIn' mode='get']"]

<p class="anonymous">I DON'T have a session.</p>

[/Plugin:NotEquals]

alex-arriaga August 18, 2016

Update Node.js using the terminal

GNU/Linux, Mac OSX, Node.js No Reply

These are just the steps to update Node.js by using your terminal:

sudo npm cache clean -f
sudo npm install -g n

1 2	sudo npm cache clean -f sudo npm install -g n

The n package represents a Node helper, and running this command upgrades node to the latest stable version.

sudo n stable

1	sudo n stable

Just to confirm we can check our version:

node -v

// Output
v6.3.1

node -v

// Output

v6.3.1

What would you like to know about?

The Problem

The Solution

The Problem

The Solution

The Problem

Solution

Be on time

Web Development and Enterprise Consulting is Exciting but Hard

Be patient

But have your plan B ready, in case you don’t get what you expect

Be prepared to travel

Being a senior professional is also understanding your company will need you

Be ready to learn

Our area is a fast-evolving zone, nothing is static, everything is being constantly improved

Be aware of hierarchies

They exist, you cannot remove them, but you can play nicely with them

Be an active listener

Stay alert, listen your team and go to the action even if it wasn’t requested

The challenge

The solution

Explanation

Otherwise plugin restrictions

Useful PM2 commands

Explanation

Join me, have fun and learn!

Tag Cloud

Recent Posts

Recent Comments

Join me, have fun and learn!

Recent Posts

Day quote…

Recent Comments

Categories

Tag Cloud

Archives

Join me, have fun and learn!

Recent Posts

Archives

Tag Cloud

Recent Comments

Categories