Hellow World, JS

“Hello World” is a classic program that is often used as a simple introduction to programming languages. In this tutorial, we’ll show you how to create a “Hello World” program in JavaScript, one of the most widely used programming languages on the web. JavaScript is a versatile and powerful language that is used to create interactive and dynamic web pages. By learning how to create a “Hello World” program in JavaScript, you’ll gain a foundational understanding of the language and its syntax.

You’ll also learn how to use one of the built-in functions in JavaScript, which will be useful in future programming projects. This tutorial is aimed at beginners who are new to JavaScript and programming in general. By the end of the tutorial, you’ll have created a simple “Hello World” program that displays a message to the user. This program can serve as a starting point for more complex projects, and it will help you gain the skills and knowledge needed to become a proficient JavaScript developer.

Hello World Example and Files

index.html Explanation

Click on the Show Files button, then on the index.html file.  JavaScript connects to the page via the <script> tag that’s included in the <body> section of the HTML code, typically placed before the closing body tag. The <script> tag specifies the URL of the JavaScript file that contains the code that should be executed when the page loads. In this case, the URL of the JavaScript file is “script.js”, so the browser will look for a file called “script.js” in the same directory as the HTML file. When the browser finds the JavaScript file, it will load and execute its contents.

It’s worth noting that the placement of the <script> tag can affect when and how the JavaScript code is executed. In this example, the <script> tag is included at the end of the <body> section, which means that the JavaScript code will be executed after the HTML content has loaded. This can be useful if the JavaScript code needs to manipulate the contents of the page. Alternatively, the <script> tag can be included in the <head> section of the HTML code, which means that the JavaScript code will be executed before the HTML content has loaded. This can be useful if the JavaScript code needs to set up some global variables or functions that will be used throughout the page.

The <script> tag is an essential tool for connecting JavaScript code to an HTML page, and it allows developers to create dynamic and interactive web pages that respond to user input and provide a rich user experience.

script.js Explanation

Click on the Show Files button, then on the script.js file.  The first line of this code initializes a variable named js with the value of 'amazing'. In JavaScript, you can use the let keyword to declare a variable that is scoped to the block where it is declared. In this case, the js variable is declared at the top level of the script, so it is accessible anywhere in the script.

The second line of the code uses an if statement to check if the value of the js variable is equal to 'amazing'. In JavaScript, you can compare values using the === operator, which checks for both value and type equality. If the value of js is indeed 'amazing', the code block within the curly braces {} will be executed. Within the if code block, we have an alert statement that displays a message in a popup dialog box. The message says 'Hello World! This is JS'. The alert function is a built-in JavaScript function that displays an alert box with a message to the user.

Finally, we have a comment that provides some information about the JavaScript console. The console is a tool that is built into most web browsers, and it allows developers to view and interact with the JavaScript code that is running on a web page. In this case, the comment is simply letting us know that we can perform mathematical calculations within the console.

Overall, this code sample provides a very basic introduction to some key concepts in JavaScript, such as variables, conditional statements, and functions. It also demonstrates how to display messages to the user using the alert function, which can be a useful debugging tool. By building on these concepts, you can begin to develop more complex JavaScript programs and applications.