“JavaScript Rules!” in JavaScript

As with any programming language, the first thing to do is write and execute some “Hello World!” program.

The goal of the “Hello World!” program is to introduce you to the language, and prove that it works. The Hello World program is essentially a way to make sure you are up and running.

Browser Recommendation

Before we proceed, let’s quickly add a note on tools and technologies. All examples for this course will be tested and demoed with Google’s Chrome browser. I would suggest you download, install, and use Chrome for this course.

A Series of Statements

Since JavaScript is a full-fledged programming language, it behaves differently than the markup language of HTML or the styling language of CSS. The significant difference is that JavaScript executes a series of statements. Every “chunk” of code that does something unique is a statement. JavaScript executes these statements in order, starting at the top of a file, and working its way down.

Executing Statements in the Browser

Every modern web browser built for computers (as opposed to mobile devices/OS’s) includes a “web console”. This console does several things, including;

• post errors about the site
• print out information developers tell it to
• allow for interactive JavaScript statements to be executed via the “command line”

For our first “Hello World!” program, we will use Chrome’s “Web Console.”

To open the Web Console (Ctrl+Shift+I on Windows and Linux or Cmd-Option-K on Mac), select the three vertical ellipses from the upper right hand corner of the browser. Then, select “More TOols” and then “Developer Tools” in Chrome. By default, it will open a new window to the right or bottom of the browser window. Along the bottom of the console is a command-line that you can use to enter JavaScript, and the output appears in the pane above:

Our First Program

To write and execute our first “JavaScript Rules!” program, you should type the following into the command line of the web console, then hit return on your keyboard.

console.log("JavaScript Rules!");

After pressing return, you should see “JavaScript Rules!” printed to the web console window.

CONGRATULATIONS, YOU HAVE WRITTEN YOUR FIRST PROGRAM FOR THIS COURSE!!!!

What is Happening

In this “JavaScript Rules!” program, there are a couple of things happening. We will discuss these in greater detail in the coming weeks.

For the moment, I will tell you that you have written a statement that uses a function (console.log()) that prints directly to the JS web console.

Within that console.log function, you included a string as the sole input parameter.

A string is any set of text, comprising letters, numbers, and special characters (i.e., &%^). Strings are always surrounded by matching single (') or double (") quotation marks.

A parameter is a value, which is passed to a function for the function to do something with it.

In essence, the program you wrote and executed told the JavaScript engine to print the string "JavaScript Rules!" to the JS web console output.

Working with the Web Console

Many of the techniques and concepts discussed in the next few weeks will be capable of being explored through the command line of the web console. I would encourage you to use this tool as a playground for exploring JavaScript, how it works, what is possible, and trying new concepts.