ProgressEvent

ProgressEvent()

Creates aProgressEventevent with the given parameters.

Also inherits properties from its parentEvent.

ProgressEvent.lengthComputableRead only

A boolean flag indicating if the ratio between the size of the data already transmitted or processed (loaded), and the total size of the data (total), is calculable. In other words, it tells if the progress is measurable or not.

ProgressEvent.loadedRead only

A 64-bit unsigned integer indicating the size, in bytes, of the data already transmitted or processed. The ratio can be calculated by dividingProgressEvent.totalby 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. Note that for compressed requests of unknown total size,loadedmight contain the size of the compressed, or decompressed, data, depending on the browser. As of 2024, it contains the size of the compressed data in Firefox, and the size of the uncompressed data in Chrome.

ProgressEvent.totalRead only

A 64-bit unsigned integer indicating the total size, in bytes, of the data being transmitted or processed. When downloading a resource using HTTP, this value is taken from theContent-Lengthresponse header. It only counts the body of the HTTP message, and doesn't include headers and other overhead.

Inherits methods from its parent,Event.

The following example adds aProgressEventto a newXMLHTTPRequestand uses it to display the status of the request.

constprogressBar=document.getElementById("p"),
client=newXMLHttpRequest();
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();

• TheEventbase interface.