The XMLHttpRequestEventTarget.onerror is the function called when an XMLHttpRequest transaction fails due to an error.

API Event Handler Property Reference Web XMLHttpRequestEventTarget

The XMLHttpRequestEventTarget.onload is the function called when an XMLHttpRequest transaction completes successfully.

API Event Handler Property Reference Web XMLHttpRequestEventTarget

The XMLHttpRequestEventTarget.onloadstart is the function called when an XMLHttpRequest transaction starts transferring data.

API Event Handler Property Reference Web XMLHttpRequestEventTarget

The XMLHttpRequestEventTarget.onprogress is the function called periodically with information when an XMLHttpRequest before success completely .

Event Handler Property Reference Web XHR XMLHttpRequestEventTarget