onChange JavaScript (JS) Example: HTML DOM Objects – Event – onChange JavaScript (JS) Example
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onChange JavaScript (JS) Example: HTML DOM Objects – Event – onChange JavaScript (JS) Example
Purpose: – Illustrates the JavaScript syntax for the onChange Event.
Prerequistes:
- Install Visual Web Developer 2008
Syntax: Object.onChange="yourjavascriptcode()" – Allows you to know when text or selection for element has changed.
Restrictions: None
Notes:
- You can build your own library of syntax examples by using same web site over and over and just add new files to it.
Instructions:
- Use Visual Web Developer 2008
- Create new web site;
- Click File/New Web Site
- Select ASP.NET Website Template
- Select C-Sharp for language
- name of Web Site could be JavaScript_Syntax.
- Add New folder named "HTMLDOMObjects"
- Right-click project name in solution explorer;
- add new folder;
- name of folder should be: HTMLDOMObjects
- Add New subfolder to "HTMLDOMObjects" folder named "DOMEvent"
- Right-click folder named "HTMLDOMObjects" in solution explorer;
- add new folder;
- name of folder should be: DOMEvent
- Add New subfolder to "DOMEvent" subfolder named "EventHandlers"
- Right-click subfolder named "DOMEvent" in solution explorer;
- add new folder;
- name of folder should be: EventHandlers
- Add HTML Page Named onChange to EventHandlers subfolder
- Right-click EventHandlers subfolder;
- add new item;
- Select HTML Page
- HTML Page name should be onChange
- Click on copy code in code below to copy code into HTML Page onChange.htm
- Right-click on HTML page onChange.htm and select view in browser
| HTML | | copy code | | ? |
< !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> |
<html> |
<head> |
<title>IdealProgrammer.com: onChange </title> |
<!-- |
*************************************************** |
* This example is from http://idealprogrammer.com * |
*************************************************** |
//***************************************************** |
// DOM Objects |
//***************************************************** |
//***************************************************** |
// *** DOM Event - EventHandlers *** |
//***************************************************** |
//***************************************************** |
// onChange |
//***************************************************** |
// SYNTAX: |
// object.onChange="yourjavascriptcode()" Allows you to know when object |
// text has been changed |
================================================================= |
An EXCELLENT tutorial on event basics can be found at: |
http://www.quirksmode.org/js/introevents.html |
================================================================= |
You can access the following properties thru the event handler: |
Available Properties |
altKey Retrieves a value that indicates the state of the ALT key. |
altLeft Retrieves a value that indicates the state of the left ALT key. |
clientX Sets or retrieves the x-coordinate of the mouse pointer's position relative to the client area of the window, excluding window decorations and scroll bars. |
clientY Sets or retrieves the y-coordinate of the mouse pointer's position relative to the client area of the window, excluding window decorations and scroll bars. |
ctrlLeft Sets or retrieves the state of the left CTRL key. |
offsetX Sets or retrieves the x-coordinate of the mouse pointer's position relative to the object firing the event. |
offsetY Sets or retrieves the y-coordinate of the mouse pointer's position relative to the object firing the event. |
returnValue Sets or retrieves the return value from the event. |
screenX Sets or retrieves the x-coordinate of the mouse pointer's position relative to the user's screen. |
screenY Sets or retrieves the y-coordinate of the mouse pointer's position relative to the user's screen. |
shiftLeft Retrieves the state of the left SHIFT key. |
srcElement Sets or retrieves the object that fired the event. |
type Sets or retrieves the event name from the event object. |
x Sets or retrieves the x-coordinate (in pixels) of the mouse pointer's offset from the closest relatively positioned parent element of the element that fired the event. |
y Sets or retrieves the y-coordinate (in pixels) of the mouse pointer's offset from the closest relatively positioned parent element of the element that fired the event. |
The captureEvents() method captures all the events of the event type passed. |
When you have multiple events to capture, separate them with the pipe, |, character. |
Here are the types of event you can capture: |
Event.ABORT |
Event.BLUR |
Event.CHANGE |
Event.CLICK |
Event.DBLCLICK |
Event.DRAGDROP |
Event.ERROR |
Event.FOCUS |
Event.KEYDOWN |
Event.KEYPRESS |
Event.KEYUP |
Event.LOAD |
Event.MOUSEDOWN |
Event.MOUSEMOVE |
Event.MOUSEOUT |
Event.MOUSEOVER |
Event.MOUSEUP |
Event.MOVE |
Event.RESET |
Event.RESIZE |
Event.SELECT |
Event.SUBMIT |
Event.UNLOAD |
--> |
<script type="text/javascript"> |
function writeAvailableProperties() { |
document.write(event.altkey + " - altKey Retrieves a value that indicates the state of the ALT key.<br />"); |
document.write(event.clientX + " - clientX Sets or retrieves the x-coordinate of the mouse pointer's position relative to the client area of the window, excluding window decorations and scroll bars.<br /><div style='background-color:Yellow;border-color:black;border-style:solid;border-width:1px;'> Please use browser back button to return to previous page</div><br /><br />"); |
} |
function doSomething(e) { |
if (!e) var e = window.event |
// e refers to the event |
document.write(e.clientY + " - clientY Sets or retrieves the y-coordinate of the mouse pointer's position relative to the client area of the window, excluding window decorations and scroll bars.<br /><br /><div style='background-color:Yellow;border-color:black;border-style:solid;border-width:1px;'> Please use browser back button to return to previous page</div><br /><br />"); |
} |
</script> |
</head> |
<body> |
<h1>Change Text Fields and Select from DropDown to see onChange in Action</h1> |
<input type="text" |
name="txtState" |
value="State" |
onchange="alert(event.srcElement.name + '\n' + event.srcElement.type)" /><br /> |
<input type="text" |
name="txtCountry" |
value="Country" |
onchange="writeAvailableProperties()" /><br /> |
<input type="text" id="idZip" |
name="txtZip" |
value="Zip" /> |
<script type="text/javascript"> |
idZip.onchange = doSomething; |
if (idZip.captureEvents) idZip.captureEvents(Event.CHANGE); |
</script> |
<p>Select a different option in the drop-down list box to trigger the onchange event.<br /> |
<select name="Groceries" id="idGroceries" > |
<option value="Fruit">Fruit</option> |
<option value="Meat">Meat</option> |
<option value="Vegatables">Vegatables</option> |
</select> </p> |
<script type="text/javascript"> |
// This is the "traditional" and recommended technique for registering an event |
// handler because it allows you to separate structure from behavior; the |
// "inline" method of registering an event within xhtml tags is not |
// the recommended approach because it blurs structure and behavior. |
// For complete explanation, please see the following excellent article: |
// http://www.digital-web.com/articles/separating_behavior_and_structure_2/ |
// |
// Note: Using getElementById so registering event will work in FireFox |
// |
var mySelect = document.getElementById("idGroceries"); |
mySelect.onchange = doSomething; |
if (mySelect.captureEvents) mySelect.captureEvents(Event.CHANGE); |
</script> |
</body> |
</html> |
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