The first step in running a JavaScript program is creating a
file that contains the definitions of the functions, along with
comments that give human readers a better understanding of
what the program does.
• Here, for example, is the complete HelloWorld.js file:
/*
* File: HelloWorld.js
* -------------------
* This program displays "hello, world" on the console. It
* is inspired by the first program in Brian Kernighan and
* Dennis Ritchie's classic book, The C Programming Language.
*/
function HelloWorld() {
console.log("hello, world");
}
Creating the HTML File (Version 1)
- A simple HTML file that loads the HelloWorld.js program looks like this:
<!DOCTYPE html>
<html>
<head>
<title>Hello World</title>
<script type="text/javascript" src="HelloWorld.js"></script>
</head>
<body onload="HelloWorld()"></body>
</html>
- This file asks the browser to load the file HelloWorld.js and then call the function HelloWorld once the page is loaded.
- The problem with this strategy is that it is hard "to find out where your output went" as Kernighan and Ritchie advise.
Creating the HTML File (Version 2)
• The output from the console log appears in different places in
different browsers and usually requires the user to take some
explicit action before it is visible.
• To make the console log easier to find, we have provided a
library called JSConsole.js that redirects the console log to
a much more visible area of the web page.
<!DOCTYPE html>
<html>
<head>
<title>Hello World</title>
<script type="text/javascript" src="JSConsole.js"></script>
<script type="text/javascript" src="HelloWorld.js"></script>
</head>
<body onload="HelloWorld()"></body>
</html>
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