Sun, Jul
2 New Articles

Node.js on IBM i: Functions

Programming - Other
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

We have been writing and using functions all along without much commentary, so it’s time to back up and deal with them. Check out Part One of this excerpt series.  And Part Two and Part Three here.

Editor's Note: This article is excerpted from chapter 10 of Open Source Starter Guide for IBM i Developers, by Pete Helgren.

You know what functions are, so I don’t really need to explain what they are. You have been writing subroutines and subprocedures for years and, basically, those would be the equivalent of what a function is in JavaScript. Sometimes they are called functions when they stand alone, and sometimes they are called methods when encapsulated in a class or object. Basically it is a chunk of code you reference by a name and pass it parameters, except when you don’t. Functions can be named in JavaScript or anonymous. Anonymous functions have no name and are usually assigned to a variable. You see anonymous functions quite a bit in asynchronous functions like ajax (xhr) calls because the asynchronous methods usually return data or pass a callback; in those cases, naming the function would be superfluous. Let’s take a quick tour of functions in JavaScript and see what they can bring to the party.

At its simplest, a JavaScript named function will have a name, a function body, and probably a few statements to be run. A simple example would be:

Node.js on IBM i: Functions - Figure 1

You could also assign a function to a variable. When you do that, you are actually creating an anonymous function and then assigning it to the variable.

Node.js on IBM i: Functions - Figure 2

Then you could invoke it:

Node.js on IBM i: Functions - Figure 3

It would output “Hello Pete”.

We didn’t talk about “hoisting” before because it is a little weird and is probably less obvious with variables. Hoisting is JavaScript’s default behavior of moving variable (and function) declarations to the top of the script. You won’t see them move; the JavaScript runtime will “hoist” those suckers to the top. So you might see something like this in a script:

Node.js on IBM i: Functions - Figure 4

And you’d be wondering where the heck those variables are declared. Where is the rocknroll function? Well, it could be way down in the script body. I tend to be a bit more tidy than that and naturally declare my stuff that will be global or used throughout a script at the top of the script, but that doesn’t always happen. JavaScript “helps” you out by automagically moving declarations to the top. Beware the initialization weirdness that can happen! You might have code like this:

Node.js on IBM i: Functions - Figure 5

And the log statement displays “NaN” (not a number). What!? Both 5 and 7 are numbers, so why is the product of them not a number? It’s because the declaration of y is hoisted. In reality, here is what JavaScript did to “help” you:

Node.js on IBM i: Functions - Figure 5

Isn’t that helpful? That kind of stuff can drive you nuts. So, if you think you have all of your declarations correct and are seeing weird errors, take a careful look at what “hoisting” might have done to you.

So you can create functions and name them or assign them to variables. You can also have the function return some data as well, and you use a return statement to do that. We could write our sayHello function like this:

Node.js on IBM i: Functions - Figure 7

We can create an object and put a function into it:

Node.js on IBM i: Functions - Figure 8

Node.js on IBM i: Functions - Figure 8

This is a pretty good overall demonstration of a function called from an object. Once we have created the Person, we can invoke the talkAboutMe method with dotted notation from the object. Nice.

Just a few more caveats. Occasionally you might forget to indicate that you are calling a function and simply call the function without the parentheses. Doing this will get you the function definition rather than the function. Every once in a while, you’ll see a self-invoking function (illegal in three states!) that may look a little strange:

Node.js on IBM i: Functions - Figure 9

Note the parentheses () at the end invoke the function directly. Again, this is a fairly rare use case, but it is something you may trip against, nonetheless. We will see an example of this as we visit Node.js.

Are we there yet? Can we get to know Node.js a little now? Yes, now would be a good time...

Next time: Part 5 - Node.js.  Can't wait?  You can pick up Peter Helgren's book, Open Source Starter Guide for IBM i Developers at the MC Press Bookstore Today!

Peter Helgren

Peter Helgren is programmer/team lead at Bible Study Fellowship International. Pete is an experienced programmer in the ILE RPG, PHP, Java, Ruby/Rails, C++, and C# languages with more than 25 years of system 3X/AS400/iSeries/IBM i experience. He holds certifications as a GIAC certified Secure Software Programmer-Java and as an MCSE. He is currently executive vice president on the COMMON Board of Directors and is active on several COMMON committees. His passion has always been in system integration, and he focuses on open-source applications and integration activities on IBM i. Pete is a speaker/trainer in RPG modernization, open-source integration, mobile application development, Java programming, and PHP and actively blogs at petesworkshop.com.

MC Press books written by Peter Helgren available now on the MC Press Bookstore.

Open Source Starter Guide for IBM i Developers Open Source Starter Guide for IBM i Developers
Check out this practical introduction to open-source development options, including XMLSERVICE, Ruby/Rails, PHP, Python, Node.js, and Apache Tomcat.
List Price $59.95

Now On Sale



Support MC Press Online


Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: