self.context = [webView valueForKeyPath:@"documentView.webView.mainFrame.javaScriptContext"];

NSString *userName = self.userNameTextField.text;
NSString *password = self.passwordTextField.text;
NSString *verifycode = self.showVerifyCode ? self.verifyTextField.text : @"";
NSString *jscriptContent = [NSString stringWithFormat:
@"var CodeImgWatcher=setInterval('updateVerifyCodeImg()','500');
var LoginErrWatcher = setInterval('getErrInfo()','500');
document.getElementById('login-username').value = '%@';
document.getElementById('login-password').value = '%@';
document.getElementById('login-verifycode').value = '%@';
document.getElementById('login-submit').click();",
userName,password,verifycode];
[self.mainWebView stringByEvaluatingJavaScriptFromString:jscriptContent];