当请求遇到错误时提出的事件 .
| Name | Type | Description |
|---|---|---|
statusCode |
number | optional The HTTP error status code, such as 404. |
response |
object | optional 答复中包括错误. |
responseHeaders |
string | object | optional 响应头,作为对象字面或 string in the format returned by XMLHttpRequest's getAllResponseHeaders() function. |