We need to use the canGoBack method of webView, but we found that weex does not provide the export of this method
Then I found that the source code of weex sent fireEvent to the js side in the - (void)webViewDidFinishLoad:(UIWebView *)webView; method
However, when ajax refreshes the page asynchronously, the - (void)webViewDidFinishLoad:(UIWebView *)webView; method on the Native side will not be triggered, so our js side still uses the previous canGoBack value
