JavaScript A Web Script Language

Fred Durao [email protected]

Overview of JavaScript

JavaScript is primarily used in the client-side, implemented as part of a web browser in order to provide enhanced user interfaces and dynamic websites .

- Originally developed by Netscape and Sun in 1995; We’ll call collections of JavaScript code scripts, not programs; The primary use of JavaScript is to write functions that are embedded included from HTML pages. in or

Examples of JavaScript (2)

Some simple examples of this usage are:

•

Validating input values of a web form to make sure that they are acceptable before being submitted to the server.

EXAMPLE : http://www.javascript-coder.com/html-form/javascript-form-validation example.html

•

Opening or popping up a new window with programmatic control over the size, position, and attributes of the new window.

EXAMPLE : http://www.tizag.com/javascriptT/javascriptpopups.php

•

Changing images as the mouse cursor moves over them: This effect is often used to draw the user's attention to important links displayed as graphical elements. EXAMPLE : http://www.w3schools.com/js/tryit.asp?filename=tryjs_animation

General Syntactic Characteristics

JavaScript scripts ARE embedded in HTML documents in the HEAD of HTML.

- Either directly, as in - Or indirectly, as a file specified in the src --



Screen Output & Keyboard Input

- The JavaScript model for the HTML document is the Document object - The model for the browser display window is the Window object - The Window the Document object has two properties, document and window , which refer to and Window objects, respectively - The Document object has a method, write , which dynamically creates content e.g., document.write("Answer: " + result + "
"); - The parameter is sent to the browser, so it can be anything that can appear in an HTML document (
, but not \n ) - The Window object has three methods for creating dialog boxes, alert , confirm , and prompt

Screen Output

(continued) 1. alert("Hej! \n"); - Opens a dialog box which displays the parameter string and an OK button - It waits for the user to press the OK button 2. confirm("Do you want to continue?"); - Opens a dialog box and displays the parameter and two buttons, OK Cancel and 3. prompt("What is your name?", ""); - Opens a dialog box and displays its string parameter, along with a text box and two buttons, OK and Cancel Examples: http://www.w3schools.com/js/js_examples.asp

Functions

A function contains java script code that will be executed by an event call to the function.

or by a In general, we place all functions in the head of the the XHTML document Functions are declared as such: function function_name ( parameter1, parameter2, … ) { -- java script code – } OBS: parameters are optional!

EXAMPLE:

Calling Functions

A functions are called from event attributes in HTML tags.

EXAMPLE:

Example: http://www.w3schools.com/js/tryit.asp?filename=tryjs_function1

Calling Functions from HTML Event Attributes

HTML added the ability to let events trigger actions in a browser, like starting a JavaScript when a user clicks on an element.

EXAMPLE FOR MOUSE EVENTS: See complete list at: http://www.w3schools.com/tags/ref_eventattributes.asp

Javascript Reference

Tutorial:

•

http://www.w3schools.com/js/default.asp

Examples:

•

http://www.w3schools.com/js/js_examples.asp

Validation:

•

http://www.w3schools.com/js/js_form_validation.asp