What is JavaScript?
- JavaScript was designed to add interactivity to HTML pages
- JavaScript is a scripting language
- A scripting language is a lightweight programming language
- A JavaScript consists of lines of executable computer code
- A JavaScript is usually embedded directly into HTML pages
- JavaScript is an interpreted language (means that scripts execute without preliminary compilation)
- Everyone can use JavaScript without purchasing a license
Are Java and JavaScript the Same?
NO!Java and JavaScript are two completely different languages in both concept and design!
Java (developed by Sun Microsystems) is a powerful and much more complex programming language - in the same category as C and C++.
What can a JavaScript Do?
- JavaScript gives HTML designers a programming tool - HTML authors are normally not programmers, but JavaScript is a scripting language with a very simple syntax! Almost anyone can put small "snippets" of code into their HTML pages JavaScript can put dynamic text into an HTML page - A JavaScript statement like this: document.write("<h1>" + name + "</h1>") can write a variable text into an HTML page
- JavaScript can react to events - A JavaScript can be set to execute when something happens, like when a page has finished loading or when a user clicks on an HTML element
- JavaScript can read and write HTML elements - A JavaScript can read and change the content of an HTML element
- JavaScript can be used to validate data - A JavaScript can be used to validate form data before it is submitted to a server. This saves the server from extra processing
- JavaScript can be used to detect the visitor's browser - A JavaScript can be used to detect the visitor's browser, and - depending on the browser - load another page specifically designed for that browser
- JavaScript can be used to create cookies - A JavaScript can be used to store and retrieve information on the visitor's computer
How to Use Java Script in HTML
Example
<!DOCTYPE html>
<html>
<body>
<script type="text/javascript">
document.write("Hello!");
</script>
</body>
</html>
<html>
<body>
<script type="text/javascript">
document.write("Hello!");
</script>
</body>
</html>
OutPut
Hellow!
Example Explained
To insert a JavaScript into an HTML page, we use the <script>
tag. Inside the <script> tag we
use the "type=" attribute to define the scripting language.
So, the <script type="text/javascript"> and </script> tells where the JavaScript starts and ends:
<html >
<body >
<script type="text/javascript" >
...
</script >
</body >
</html >
The word document.write is a standard JavaScript command for writing output to a page.
By entering the document.write command between the<body >
<script type="text/javascript" >
...
</script >
</body >
</html >
<script> and </script> tags, the
browser will recognize it as a JavaScript command and execute the code line. In this case the
browser will write Hello World! to the page:
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