Introduction to JavaScript
JavaScript is written into an HTML document in 2 ways:
- Using:
<script type="text/JavaScript"> Where you would embed your code here </script> - Or referencing it kind of like an external CSS:
<script type="text/JavaScript" src="myJavaScript.js"></script>
Below is a very simple HTML Skeleton with our JavaScript embedded using the first method.
Example
<html>
<body>
<h3>My First JavaScript Code</h3>
<script type="text/JavaScript">
document.write("<p>Hello!</p>");
</script>
</body>
</html>Result
My First JavaScript Code
Hello!
First, let's break down document.write("<p>Hello!</p>")JavaScript is a Object Based Programming Language. So, in the example above document is the object. In JavaScript, an object followed by a . , such as document. , is an indication that a method or an property will follow. (Also, some programmers often refer to properties as attributes.)
The write here is actually one of the document's methods. Methods generally have arguments, and in this case, the <p>Hello!</p> is the argument.
Now let's understand an object's property.
Example
<html>
<body>
<h3>JavaScript Object Properties</h3>
<p>
<script type="text/JavaScript">
document.write(document.location);
</script>
</p>
</body>
</html>Result
JavaScript Object Properties
/tutorials/javascript/introduction-javascript
In this example, you can see that we use the document's property, document.location, as an argument for the method, document.write. The document.location is equal to the current URL, but since it was in the method document.write, it actually wrote that to the DOM so that we could see it.