# UploadTask.onProgressUpdate(function callback)
Start from base library version 1.4.0. Please remaining backward compatible.
Listens on the upload progress change event.
# Parameters
# function callback
The callback function for the upload progress change event.
# Parameters
# Object res
| Property | Type | Description |
|---|---|---|
| progress | number | Upload progress percentage |
| totalBytesSent | number | The length of uploaded data, in bytes |
| totalBytesExpectedToSend | number | The length of data expected to be uploaded, in bytes |