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What is JavaScript
JavaScript is an object-oriented scripting language used to enable programmatic
access to computational objects within a host environment. Although also used in
other applications, it is primarily used in the form of client-side JavaScript,
implemented as part of a web browser, providing enhanced user interfaces and
dynamic websites. JavaScript support is built right into web browsers. Provided
that the visitors to your site are using web browsers that support JavaScript
(most do) and have JavaScript enabled (it is by default) then your JavaScript
will run.
Differences of JavaScript and Java
There are many differences between Java and JavaScript language as
| JavaScript |
Java |
| Interpreted by client mainly |
Compiled on server and changes it in
HTML and user gets only HTML coding as in ASP, PHP etc languages.
Because user's browser only reads HTML and JavaScript coding. |
| Object-based language because it has
no class or inheritance features |
Object-oriented and it has class or
inheritance features. |
| It has no graphics capabilities |
It has high graphic capabilities |
| It can't read or write files |
It can read and write files |
| It has no networking support like can
not let us to chat or communicate within network computers using bind(),
listed() or send() properties |
It has all networking support |
History of JS
When World Wide Web created in early 1990s all web pages were static. When we
view the web page on internet we exactly saw what the page was set up to show.
Netscape was the first to bring out a programming language that would allow web
pages to become interactive - they called it LiveScript and it was integrated
into the browser. The programming language called Java became very well known
and so Netscape decided to cash by renaming the language to JavaScript what they
have created for Netscape Navigator browsers. At the time Netscape Navigator was
by far the more popular browser and so later versions of Internet Explorer
implemented versions of Jscript and vbScript that were more and more like
JavaScript. It is very big cause not to support all script commands by all the
browsers. Although scripting language was too great to deal its future
developments so in 1996 JavaScript was handed over to an international standards
body called ECMA who then became responsible for the subsequent development of
the language. As a result of this the language was officially renamed ECMAScript
or ECMA-262 but most people still refer to it as JavaScript.
Function of JS
JavaScript is a client-side programming language meant for use on the web and
when you request for any page on web script coding automatically runs on our
computer because our browser have the ability to read JS coding. Client-Side
scripting language means which runs on user's computer and Server-Side scripting
language means, which runs on server computer from where the web pages are
requested.
Where to write the JavaScript Program
JavaScript is an interpreted language and so no special program is required. Any
plain text editor such as Notepad is quite satisfactory for being able to write
JavaScript. That said, an editor, which colorizes the code to make it easier to
see what is what makes it easier to find your mistakes. An editor named Komodo
will be nice for to write JavaScript coding.
Difference between HTML and JavaScript
HTML and JavaScript are two completely different things. HTML is a mark-up
language designed for defining static web page content. JavaScript is a
programming language designed for performing dynamic tasks.
Features of JavaScript
There are lots of features as listed below: - A Great Programming tool for HTML
Professional Web designers are undoubtedly adept in using HTML because
JavaScript is a powerful scripting language that helps HTML designers to
effectively and interactively design websites and web pages in a very simple and
efficient way.
- Handles Dynamic Effects
JavaScript is such a powerful scripting language, which has features to achieve
dynamic effects in web pages. Using the features available in JavaScript, the
designer can decide to have dynamically placed text at run time.
- Browser Detection
One of the powerful features of JavaScript is its ability to detect client side
browser. Browser detection feature of JavaScript helps to achieve independent
platforms. JavaScript can detect the type of browser the visitor is using and
programmatically switch the page to show customised pages designed for different
browsers. Thus by making use of browser detection feature of JavaScript, the
designer gets better control over the browser.
- Time Savings
JavaScript also has the feature of validating data submitted at the client
level. This helps in saving the processing time of the server because JavaScript
initially creates the validation on the client side.
- Interpreted Language
It is an interpreted language, meaning that it can be used or executed with ease
without pre-compilation.
How to use JS in web page
There are mainly two ways to use JS in web page:- Using JS commands within the web page with HTML coding
- Using JS commands from external JS file
Using JS commands within the web page with HTML coding
We use to write all codes in a same page which has the extension .htm, .html, .php,
.asp, .aspx, .cfm etc.
<html>
<head>
<title>TESTING JS</title>
<script language="JavaScript" type="text/javascript">
window.print()
</script>
</head>
<body onload="disco()">
<div> This is the content to be printed. </div>
</body>
</html>
More examples
JavaScript in head
<html>
<head>
<script type="text/javascript">
function message()
{
alert("This alert box was called with the onload event");
}
</script>
</head>
<body onload="message()">
<p>We usually use the head section for functions (to be sure that the functions
are loaded before they are called).</p>
</body>
</html>
JavaScript in HTML H1 tag
<html>
<body>
<script type="text/javascript">
document.write("<h1>Hello World!</h1>");
</script>
</body>
</html>
JavaScript in body
<html>
<body>
<script type="text/javascript">
document.write("<h1>Hello World!</h1>");
</script>
</body>
</html>
Using JS commands from external JS file(s)
To use JavaScript (.js) files in HTML page, we have to write all JavaScript
coding in a file, which has exetesion .js, and remember not use opening and
closing <SCRIPT> tags in .js files. Assume that we have myjava.js file which has
some coding, without only <SCRIPT> tags. And now to use it in HTML file write
the following code in HTML file
HTML file content
<html>
<head>
<script type="text/javascript" src="external.js">
</script>
</head>
<body onload="message()">
This text is from body
</body>
</html>
external.js file content
function message()
{
alert("This alert box was called with the onload event");
}
HAVE A HAPPY CODING!
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