Welcome!

Java IoT Authors: Liz McMillan, Elizabeth White, Yeshim Deniz, Zakia Bouachraoui, Pat Romanski

Related Topics: @DevOpsSummit, Java IoT, Microservices Expo

@DevOpsSummit: Blog Feed Post

Node.js ABCs - L Is for Loading | @DevOpsSummit #DevOps

A great benefit of utilizing a language like Node.js is the wide assortment of 3rd party modules that are at your disposal

One of the great benefits of utilizing a language like Node.js is the wide assortment of 3rd party modules that are at your disposal.  From calculating the validity of credit card numbers, to managing network connections, the Node Package Manager (npm) repository has hundreds of thousands of packages available to you.  This article will explain how you can load modules into your project.

Loading and Referencing a Module
In Node.js, modules are accessed either by their name or the file path on the system.  Non-system modules referenced by name will eventually be mapped into a file system path.

Each module exposes a public interface that can be used after the module is imported with the "require" into the current script.

var mod = require("some_module_name");

LoadingDockEquipment

The previous command will import and return an object that represents the external API exposed by the module.  The value of that object is dependent on the module and can include an object, an array, a function, or any other type of JavaScript object.

Developing and Exporting Modules
For the module developer, you must use the CommonJS Module System to make your modules available to the outside world.  Let's create a sample module “person.js” that exports a Person constructor.

/* File person.js */
function Person(name) {
var _name = name;
function name() {
return _name;
}
}
module.exports = Person;

In the above example, the Person function is defined and then specified with the "module.exports" object that the module will export to other scripts that require this module.

As mentioned above, more complex objects can be exported by adding onto the module.exports object with whatever values you deem fit for your module.

/* file mymodule.js */
function sayHi() { console.log("HI!!!"); }
function sayBye() { console.log("BYE!!!"); }
module.exports.sayHi = sayHi;
module.exports.sayBye = sayBye;

Below is the code to load the module and call the sayHi and sayBye functions.

var mymodule = require("./mymodule");
mymodule.sayHi();
HI!!!
mymodule.sayBye();
BYE!!!

Loading a Module
There are a couple of ways to reference modules depending on their kind.  There are core modules, 3rd party modules, or local modules.

Core Modules
Since core modules are part of the distribution, you need only refer to it by it's name (not the path).  Core modules with name collisions to local modules take precedence.  The following line will load a instance of the core "http" module.

var http = require('http');

File Module
A file module is a one that is defined in a single file on the file system.  The person.js example above is an example of a file module.  When loading a file module, you supply a path (full or relative) to the module file, optionally omitting the .js extension.

var mymodule = require("/home/joe/node/modules/mymodule");
var mymodule = require("./mymodule");

In those examples the loader will look for a file named "mymodule.js" in the specified directory.

Folder Modules
Like a file module, when loading a folder module, you specify the absolute or relative location of the folder.  The Node loader will assume this folder is a package and attempt to look for a package definition file (package.json) in which the name and location of the module file are located.  If no package.json file exists, the Node loader will look for a file named index.js.

Loader search procedure
If the module name is not a path and is not a core module, the loader will attempt to find it inside the special "node_modules" folder.  If the module doesn't exist there, it will continue up the path, folder by folder, looking within node_modules folders on those directories until either finds the module or hits the root of the file system.

Conclusion
That's about all there is to it for exporting and loading a Node.js module.  Creating modules is as easy as writing the module code and specifying what is returned with the module.exports object.  Then a simple call to require("module") is all the client has to write to make use of it.

Read the original blog entry...

More Stories By Joe Pruitt

Joe Pruitt is a Principal Strategic Architect at F5 Networks working with Network and Software Architects to allow them to build network intelligence into their applications.

IoT & Smart Cities Stories
@CloudEXPO and @ExpoDX, two of the most influential technology events in the world, have hosted hundreds of sponsors and exhibitors since our launch 10 years ago. @CloudEXPO and @ExpoDX New York and Silicon Valley provide a full year of face-to-face marketing opportunities for your company. Each sponsorship and exhibit package comes with pre and post-show marketing programs. By sponsoring and exhibiting in New York and Silicon Valley, you reach a full complement of decision makers and buyers in ...
Two weeks ago (November 3-5), I attended the Cloud Expo Silicon Valley as a speaker, where I presented on the security and privacy due diligence requirements for cloud solutions. Cloud security is a topical issue for every CIO, CISO, and technology buyer. Decision-makers are always looking for insights on how to mitigate the security risks of implementing and using cloud solutions. Based on the presentation topics covered at the conference, as well as the general discussions heard between sessio...
While the focus and objectives of IoT initiatives are many and diverse, they all share a few common attributes, and one of those is the network. Commonly, that network includes the Internet, over which there isn't any real control for performance and availability. Or is there? The current state of the art for Big Data analytics, as applied to network telemetry, offers new opportunities for improving and assuring operational integrity. In his session at @ThingsExpo, Jim Frey, Vice President of S...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settl...
The Internet of Things is clearly many things: data collection and analytics, wearables, Smart Grids and Smart Cities, the Industrial Internet, and more. Cool platforms like Arduino, Raspberry Pi, Intel's Galileo and Edison, and a diverse world of sensors are making the IoT a great toy box for developers in all these areas. In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists discussed what things are the most important, which will have the most profound e...
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, compared the Jevons Paradox to modern-day enterprise IT, examin...
Rodrigo Coutinho is part of OutSystems' founders' team and currently the Head of Product Design. He provides a cross-functional role where he supports Product Management in defining the positioning and direction of the Agile Platform, while at the same time promoting model-based development and new techniques to deliver applications in the cloud.
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
LogRocket helps product teams develop better experiences for users by recording videos of user sessions with logs and network data. It identifies UX problems and reveals the root cause of every bug. LogRocket presents impactful errors on a website, and how to reproduce it. With LogRocket, users can replay problems.
Rafay enables developers to automate the distribution, operations, cross-region scaling and lifecycle management of containerized microservices across public and private clouds, and service provider networks. Rafay's platform is built around foundational elements that together deliver an optimal abstraction layer across disparate infrastructure, making it easy for developers to scale and operate applications across any number of locations or regions. Consumed as a service, Rafay's platform elimi...