Friday, 7 January 2011

Javascript: Introduction

Javascript is a scripting language used to enhance interactivity to HTML. It is able to detect various events such as onClick (when user clicks on a button or any HTML element), onChange (when user selects a value from a drop down or list box), onBlur (when user clicks outside the HTML element or lost focus), onKeyUp (when user presses a key and releases it) and onKeyDown (when a user presses the keyboard). 


It is also used to control the design of the HTML webpage. This is used together with the events mentioned above. A web designer can use it to control how HTML elements are being displayed on the webpage. It can automatically converts all text that are typed in to uppercases. If a user clicks on a drop down value, the web developer can display those elements that needs to be shown and hide the others.


It can also be used to get the values of a textbox or a drop down or field by using Javascript methods which will be discussed later.


It can be added into the HTML page directly or linked to an external Javascript file (.js). Below is an example of how Javascript is added to the HTML code:


<script type="text/javascript">
    // add javascript coding here.
</script>


Javascript can also be placed to an external file. This is separate the HTML code with the Javascript code. It also enhances the performance of the webpage. The Javascript file will be cached and thus reduces the loading time. It can be linked from HTML to the external Javascript using this code below. For example, my external script name is test.js.


<script type="text/javascript" src="test.js"></script>


Other references:
  1. W3Schools:Javascript Tutorial
  2. Internet.com: How to place Javascripts in External Files

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