Updated HTML posts because one was kinda of short
-wave
Sunday, 22 January 2012
JavaScript
Sorry it's been a while since i've posted last , had alot of work to do and with the day of #opsony here i have had little time to write.
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Before learning JavaScript you should have basic knowledge of HTML and CSS . I guess you could learn this first but it would be really hard.
Note: Java and JavaScript are two totally different languages
A few basic facts on JavaScript
What Can 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 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
Writing to The HTML Document
The example below writes a <p> element with current date information to the HTML document:
<html>
<body>
<h1>My First Web Page</h1>
<script type="text/javascript">
document.write("<p>" + Date() + "</p>");
</script>
</body>
</html>
Changing HTML Elements
The example below writes the current date into an existing <p> element:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo"></p>
<script type="text/javascript">
document.getElementById("demo").innerHTML=Date();
</script>
</body>
</html>
Examples Explained
To insert a JavaScript into an HTML page, use the <script> tag.
Inside the <script> tag use the type attribute to define the scripting language.
The <script> and </script> tells where the JavaScript starts and ends:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo">This is a paragraph.</p>
<script type="text/javascript">
... some JavaScript code ...
</script>
</body>
</html>
The lines between the <script> and </script> contain the JavaScript and are executed by the browser.
In this case the browser will replace the content of the HTML element with id="demo", with the current date:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo">This is a paragraph.</p>
<script type="text/javascript">
document.getElementById("demo").innerHTML=Date();
</script>
</body>
</html>
---------------------------------------------------------------------------------------
Before learning JavaScript you should have basic knowledge of HTML and CSS . I guess you could learn this first but it would be really hard.
Note: Java and JavaScript are two totally different languages
A few basic facts on JavaScript
- JavaScript was designed to add interactivity to HTML pages
- JavaScript is a scripting language
- A scripting language is a lightweight programming language
- JavaScript is usually embedded directly into HTML pages
- JavaScript is an interpreted language (means that scripts execute without preliminary compilation)
What Can 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 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
Writing to The HTML Document
The example below writes a <p> element with current date information to the HTML document:
<html>
<body>
<h1>My First Web Page</h1>
<script type="text/javascript">
document.write("<p>" + Date() + "</p>");
</script>
</body>
</html>
Changing HTML Elements
The example below writes the current date into an existing <p> element:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo"></p>
<script type="text/javascript">
document.getElementById("demo").innerHTML=Date();
</script>
</body>
</html>
Examples Explained
To insert a JavaScript into an HTML page, use the <script> tag.
Inside the <script> tag use the type attribute to define the scripting language.
The <script> and </script> tells where the JavaScript starts and ends:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo">This is a paragraph.</p>
<script type="text/javascript">
... some JavaScript code ...
</script>
</body>
</html>
The lines between the <script> and </script> contain the JavaScript and are executed by the browser.
In this case the browser will replace the content of the HTML element with id="demo", with the current date:
<html>
<body>
<h1>My First Web Page</h1>
<p id="demo">This is a paragraph.</p>
<script type="text/javascript">
document.getElementById("demo").innerHTML=Date();
</script>
</body>
</html>
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