The XMLHttpRequest.upload property returns an XMLHttpRequestUpload object, representing the upload process. It is an opaque object, but being an XMLHttpRequestEventTarget, event listeners can be set on it to track its process.
Event listeners that can be triggered on an upload object are the following:
| Event listeners | Data type of response property |
onloadstart |
The fetch starts |
onprogress |
Data transfer is going on |
onabort |
The fetch operation was aborted |
onerror |
The fetch failed |
onload |
The fetch succeeded |
ontimeout |
The fetch operation didn't complete by the timeout the author specified |
onloadend |
The fetch operation completed (either success or failure) |
Specifications
| Specification | Status | Comment |
|---|---|---|
| XMLHttpRequest | Living Standard | WHATWG living standard |