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JavaScript is used in millions of Web pages to improve the design, validate forms, detect browsers, create cookies, and much more.
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JavaScript is the most popular scripting language on the internet, and works in all major browsers, such as Internet Explorer, Mozilla, Firefox, Netscape, and Opera.
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JavaScript does not provide the range of capabilities of standard programming languages. The Web developer is most likely to need to make Web pages interactive and dynamic.
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It is important to know JavaScript codes are case sensitive; you cannot indiscriminately use upper- and lower-case notation.
Your JavaScript code is open to the public.
About Web Scripting Language
Server-Side comprises the following languages
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Active Server Pages (ASP)
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Java Server Pages (JSP)
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Cold Fusion
Client Side comprises the following languages
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JavaScript
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JScript
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VBScript
The Real Name is ECMAScript
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JavaScript’s official name is “ECMAScript”. The standard is developed and maintained by the ECMA organisation.
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ECMA-262 is the official JavaScript standard. The standard is based on JavaScript (Netscape) and JScript (Microsoft).
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The language was invented by Brendan Eich at Netscape (with Navigator 2.0), and has appeared in all Netscape and Microsoft browsers since 1996.
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The development of ECMA-262 started in 1996, and the first edition of was adopted by the ECMA General Assembly in June 1997.
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The standard was approved as an international ISO (ISO/IEC 16262) standard in 1998.
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The development of the standard is still in progress.
Note:- About ECMA
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JavaScript was designed to add interactivity to HTML pages since HTML is FLAT Language, No Programming Tools available.
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JavaScript is a scripting language
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A scripting language is a lightweight programming language
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A JavaScript consists of lines of executable computer code
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A JavaScript is usually embedded directly into HTML pages
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JavaScript is an interpreted language (means that scripts execute without preliminary compilation)
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Everyone can use JavaScript without purchasing a license
NO!
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Java is Obeject Oriented Programming Language while JavaScript is Object based Scripting Language.
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Java and JavaScript are two completely different languages in both concept and design.
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Java (developed by Sun Microsystems) is a powerful and much more complex programming language – in the same category as C++ and C#.
JavaScript code can do any of the following
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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
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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
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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
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JavaScript can read and write HTML elements : A JavaScript can read and change the content of an HTML element
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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
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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
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JavaScript can be used to create cookies : A JavaScript can be used to store and retrieve information on the visitor’s computer.
JavaScript code cannot do any of the following
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use printers or other devices on the user’s system or the client-side LAN
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directly access files on the user’s system or the client-side LAN ; the only exception is the access to the browser’s cookie files.
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directly access files on the Web server.
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implement multiprocessing or multithreading.
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If you do need to access files or perform other “privileged” operations, you can use JavaScript in combination with a Java applet. Signed Java applets are allowed to do “privileged” things, and your JavaScript programs can exchange information with applets. However, you have to bear in mind the biggest JavaScript/Java limitation:- the user can always disable Java or JavaScript or both!
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access any database.
Different ways to include JavaScript in HTML Code
JavaScripts in a page will be executed immediately while the page loads into the browser. This is not always what we want. Sometimes we want to execute a script when a page loads, other times when a user triggers an event.
Scripts in the head section
Scripts to be executed when they are called, or when an event is triggered, go in the head section. When you place a script in the head section, you will ensure that the script is loaded before anyone uses it.
<html>
<head>
<em><script type="text/javascript">
//statements...
</script></em>
</head>
</html>
Scripts in the body section
Scripts to be executed when the page loads go in the body section. When you place a script in the body section it generates the content of the page.
<html><head></head>
<body>
<em><script type="text/javascript">
//statements...
</script></em>
</body></html>
Scripts in both the body and the head section
You can place an unlimited number of scripts in your document, so you can have scripts in both the body and the head section.
<html><head>
<em><script type="text/javascript">
//statements...
</script></em>
</head><body>
<em><script type="text/javascript">
//statements...
</script></em>
</body>
Using an External JavaScript
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Sometimes you might want to run the same JavaScript on several pages, without having to write the same script on every page.
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To simplify this, you can write a JavaScript in an external file. Save the external JavaScript file with a .js file extension.
Note: The external script cannot contain the <script> tag!
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To use the external script, point to the .js file in the “src” attribute of the <script> tag:
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Note: Remember to place the script exactly where you normally would write the script!
<html><head>
<em><script src="tom.js"></script></em>
</head>
<body></body></html>
JavaScript Statements
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JavaScript is a sequence of statements to be executed by the browser.
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The word document.write is a standard JavaScript command for writing output to a page.
Note:- Click here to get the Support of JavaScript with Different Browsers
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