# RequestTask.onHeadersReceived(function callback)
Start from base library version 2.1.0. Please remaining backward compatible.
Listens on HTTP Response Header event, which will be earlier than the request completion event.
# Parameters
# function callback
The callback function for the HTTP Response Header event.
# Parameters
# Object res
| Property | Type | Description |
|---|---|---|
| header | Object | HTTP Response Header returned by the developer server |