ProgressEvent
The ProgressEvent
interface represents events measuring progress of an underlying process, like an HTTP request (for an XMLHttpRequest
, or the loading of the underlying resource of an <img>
, <audio>
, <video>
, <style>
or <link>
).
Constructor
ProgressEvent()
-
Creates a
ProgressEvent
event with the given parameters.
Instance properties
Also inherits properties from its parent Event
.
ProgressEvent.lengthComputable
Read only-
A boolean flag indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not.
ProgressEvent.loaded
Read only-
A 64-bit unsigned integer value indicating the amount of work already performed by the underlying process. The ratio of work done can be calculated by dividing
total
by the value of this property. When downloading a resource using HTTP, this only counts the body of the HTTP message, and doesn't include headers and other overhead. ProgressEvent.total
Read only-
A 64-bit unsigned integer representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this is the
Content-Length
(the size of the body of the message), and doesn't include the headers and other overhead.
Instance methods
Inherits methods from its parent, Event
.
Examples
The following example adds a ProgressEvent
to a new XMLHTTPRequest
and uses it to display the status of the request.
js
const progressBar = document.getElementById("p"),
client = new XMLHttpRequest();
client.open("GET", "magical-unicorns");
client.onprogress = (pe) => {
if (pe.lengthComputable) {
progressBar.max = pe.total;
progressBar.value = pe.loaded;
}
};
client.onloadend = (pe) => {
progressBar.value = pe.loaded;
};
client.send();
Specifications
Specification |
---|
XMLHttpRequest Standard # interface-progressevent |
Browser compatibility
BCD tables only load in the browser
See also
- The
Event
base interface.