# onopen Event

Event Object

## Example

Create a new EventSource object, and specify the URL of the page sending the updates.
When (and if) a connection is established, output some text in a <h1> element:

var source = new EventSource("demo_sse.php");
source.onopen = function() {
document.getElementById("myH1").innerHTML = "Getting server updates";
};
Try it yourself »

## Definition and Usage

The onopen event occurs when a connection with an event source is opened.

Related events:

- onmessage - Occurs when a message is received
- onerror - Occurs when a problem occurs

For more information about Server-Sent Events, read our HTML5 Server-Sent Events Tutorial.

## Browser Support

The numbers in the table specify the first browser version that fully supports the event.

Event |  |  |  |  |
--- | --- | --- | --- | --- | ---
onopen | 9.0 | Not supported | 6.0 | 5.0 | 11.0

## Syntax

object.onopen=function(){myScript};Try it

Using the addEventListener() method:

object.addEventListener("open", myScript);Try it

Note: The addEventListener() method is not supported in Internet Explorer 8 and earlier versions.

## Technical Details

Bubbles: | No
Cancelable: | No
Event type: | Event

Event Object

### WEB HOSTING

UK Reseller Hosting

### WEB BUILDING

FREE Website BUILDER Free HTML5 Templates

### W3SCHOOLS EXAMS

HTML, CSS, JavaScript, PHP, jQuery, XML, and ASP Certifications

### SHARE THIS PAGE

### Color Picker

### HTML/CSS

HTML Tutorial HTML5 Tutorial CSS Tutorial CSS3 Tutorial Bootstrap Tutorial

### JavaScript

JavaScript Tutorial jQuery Tutorial jQuery Mobile Tutorial AngularJS Tutorial AJAX Tutorial JSON Tutorial

### Graphics

Canvas Tutorial SVG Tutorial Google Maps Tutorial

### Server Side

SQL Tutorial PHP Tutorial ASP Tutorial ASP.NET Tutorial VBScript Tutorial AppML Tutorial

### Web

Web Building Web Statistics Web Certification

### XML

XML Tutorial DTD Tutorial Schema Tutorial XML DOM Tutorial XPath Tutorial XSLT Tutorial XQuery Tutorial XSL-FO Tutorial RSS Tutorial WSDL Tutorial

### HTML/CSS

HTML Tag Reference HTML Event Reference HTML Color Reference CSS 1,2,3 Reference Bootstrap Reference

### JavaScript

JavaScript Reference HTML DOM Reference jQuery Reference jQuery Mobile Reference Google Maps Reference

### Server Side

PHP Reference SQL Reference ASP Reference VBScript Reference Razor Reference ASP.NET Reference

### XML

XML DOM Reference XSLT Reference XSL-FO Reference XPath Reference XQuery Reference Schema Reference RSS Reference SVG Reference

### HTML Charsets

HTML Character Sets HTML ASCII HTML ANSI HTML Windows-1252 HTML ISO-8859-1 HTML Symbols HTML UTF-8

### HTML/CSS

HTML Examples CSS Examples

### Browser Scripting

JavaScript Examples HTML DOM Examples jQuery Examples jQuery Mobile Examples AngularJS Examples AJAX Examples

### Server Scripting

PHP Examples ASP Examples VBScript Examples Razor Examples .NET Examples

### XML Languages

XML Examples DTD Examples XML DOM Examples XSL Examples XSLT Examples XPath Examples XQuery Examples Schema Examples RSS Examples SVG Examples