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How can I escape a string to ensure that it is a valid string literal in JS source?

I have a Qt application that embeds a web browser (QWebEngineView). I would like to call a javascript function with a string argument from the C++ application. The means of doing this is calling
page()->runJavaScript("setContent(\"hello\");");
This works in simple cases. However, if I try and load, say, a C++ source file and use that as the parameter of setContent, this will break, because I can't simply assemble the string like this:
auto js = QString("setContent(\"%1\");").arg(fileStr);
I tried the following:
fileStr = fileStr.replace('"', "\\\"");
fileStr = fileStr.replace("\n", "\\n");
But apparently this could not escape the string, I get an error when I call this javascript. How can I universally escape a long string with newlines and possible special characters so that I can construct a valid js fragment like this?

So, after some research, I came across QWebChannel which is meant for bi-directional communication between the application and the hosted webpage. The imported qwebchannel.js in the examples can be found here. From there, this is what I did:
In C++:
auto channel = new QWebChannel(this);
page()->setWebChannel(channel);
channel->registerObject("doc", Doc);
In HTML/JS:
new QWebChannel(qt.webChannelTransport,
function(channel) {
var doc = channel.objects.doc; // this is "doc" from the registerObject call
editor.setValue(doc.text);
doc.textChanged.connect(updateText); // textChanged is a signal of the class of doc.
}
);
So, even though this does not directly answer the question, what is presented here can be used to achieve the same effect.

JSONP callback in Dart

I have been trying to get basic JSONP working in Dart and I am getting stuck. Reading this blog post as well as this this blog show that I should use window.on.message.add(dataReceived); to get a MessageEvent and retrieve data from the event.
Dart complains that "There is no such getter 'message' in events". In addition, I looked up different ways of getting a MessageEvent but it seems to be something completely unrelated (WebSockets?) and is not what I actually need.
If anybody can explain what is going on and how to really use JSONP in Dart, that would be awesome!

You don't need to use what is described in the articles you point anymore. You can use dart:js :
import 'dart:html';
import 'dart:js';
void main() {
// Create a jsFunction to handle the response.
context['processData'] = (JsObject jsonDatas) {
// call with JSON datas
};
// make the call
ScriptElement script = new Element.tag("script");
script.src = "https://${url}?callback=processData";
document.body.children.add(script);
}

I recently wrote a blog post on this myself as I was running into similar problems.
I first cover a few prerequisite things like Verifying CORS Compliance and Verifying JSONP Support
I too ended up registering with the updated method:
window.onMessage.listen(dataReceived);
I then had a fairly simple method to dynamically create the script tag in Dart as well (my requirement was that I had to use Dart exclusively and couldn't touch the website source files):
void _createScriptTag()
{
String requestString = """function callbackForJsonpApi(s) {
s.target="dartJsonHandler";
window.postMessage(JSON.stringify(s), '*');
}""";
ScriptElement script = new ScriptElement();
script.innerHtml = requestString;
document.body.children.add(script);
}
I then invoked it from Dart with some simple logic that I wrapped in a method for convenience.
void getStockQuote(String tickerId)
{
String requestString = "http://finance.yahoo.com/webservice/v1/symbols/" + tickerId + "/quote?format=json&callback=callbackForJsonpApi";
ScriptElement script = new ScriptElement();
script.src = requestString;
document.body.children.add(script);
}
If you are using dart:js I find Alexandre's Answer useful and, after upvoting Alexandre, I have updated my post to include the simplified version as well:
context['callbackForJsonpApi'] = (JsObject jsonData)
{
//Process JSON data here...
};
This obviously eliminates the need for the onMessage and _createScriptTag above, and can be invoked the same as before.
I decided to keep both approaches, however, as I have noticed over time the Dart APIs changing and it seems to be a good idea to have a fallback if needed.

The syntax has changed
window.onMessage.listen(dataReceived);

Using RHINO js engine to make http requests

I'm trying to use the Mozilla/Rhino js engine to test some SOAP requests in the command line. However, none of the normal objects for making requests (XMLHttpRequest, HttpRequest) seem to be available. Why is this? Can I import libraries?

I was able to get it to work using just Rhino with the following code.
var post = new org.apache.commons.httpclient.methods.PostMethod("https://someurl/and/path/");
var client = new org.apache.commons.httpclient.HttpClient();
// ---- Authentication ---- //
var creds = new org.apache.commons.httpclient.UsernamePasswordCredentials("username", "password");
client.getParams().setAuthenticationPreemptive(true);
client.getState().setCredentials(org.apache.commons.httpclient.auth.AuthScope.ANY, creds);
// -------------------------- //
post.setRequestHeader("Content-type", "application/xml");
post.setRequestEntity(new org.apache.commons.httpclient.methods.StringRequestEntity(buildXML(), "text/plain", "ASCII" ));
var status = client.executeMethod(post);
var br = new java.io.BufferedReader(new java.io.InputStreamReader(post.getResponseBodyAsStream()));
var response = "";
var line = br.readLine();
while(line != null){
response = response + line;
line = br.readLine();
}
post.releaseConnection();

You might possibly find a library to import, you could also write your own in Java and make them available to your rhino instance, depending on how your are using it. Keep in mind Rhino is just a Javascript language engine. It doesn't have a DOM, and is not inherently 'web aware' so to speak.
However, since it sounds like you are doing this for testing/experimentation purposes, and you will probably be more productive not having to reinvent the wheel to do so, I will strongly, strongly suggest that you just download Node.js and look into the request module (for making HTTP requests) or any of the various SOAP modules.
You can do a ton more with Node.js, but you can also use it as a very simple runner for Javascript files as well. Regardless you should move away from Rhino though. It is really old and not really supported anymore, especially now that with JDK8 even the javax.script support will switch to the Nashorn engine.
UPDATE: If you really want to give it a go (and if you are prepared to monkey around with Java), you might look at this SO question and its answers. But unless you are something of a masochist, I think you'll be happier taking a different path.

I was actually able to do this using Orchestrator 5.1 with the 'Scriptable task' object to interface with the Zabbix API:
var urlObject = new URL(url);
var jsonString = JSON.stringify({ jsonrpc: '2.0', method: 'user.login', params: { user: 'username', password: 'password' }, id: 1 });
urlObject.contentType = "application/json";
result = urlObject.postContent(jsonString);
System.log(result);
var authenticationToken = JSON.parse(result).result;

Does anyone knows how to import new classes when using Javascript instead of Groovy as default scripting language in SoapUI?

I have a important piece of code that modifies my requests written Javascript, but i want to add an external jar and use it from the scripts, any suggestions? It's defined a sort of import function or something like that?

In order to use your own jars in Setup Script in SOAPUI with javascript language you must do the next steps:
With SOAPUI closed, copy your jars to SOAPUI_HOME/bin/ext.
Start SOPAUI
On the project properties select Javascript for Script Language property.
Then in the Setup Script you have to reference the full package for your java classes like (I put a sample where I decode a base64 string):
java.lang.System.out.println("-----------");
java.lang.System.out.println("SAMPLE INIT");
java.lang.System.out.println("-----------\n");
var obj = new org.apache.commons.codec.binary.Base64();
var stringb64 = new java.lang.String("dGVzdA==")
var dataDecoded = obj.decodeBase64(stringb64.getBytes());
java.lang.System.out.println("RESULT " + new java.lang.String(dataDecoded) + "\n");
java.lang.System.out.println("-----------");
java.lang.System.out.println("SAMPLE END");
java.lang.System.out.println("-----------");
If you run soapui from .bat you can see the system out on the cmd:

Take a screenshot of an iFrame

I am looking for a simple way to take a screenshot of an iFrame in my ASP page. I just couldn't achieve it with C# and I lack of knowledge of Javascript! Does anyone out there know the simple and best way to achieve this?
What I am trying to do is, I am building a website that students can log in to e-government website in my country and prove if they are continuing student with a single click so that they can get discount from our service.
Edit: The puzzle should be solved in local.

this piece of code worked for me. I hope it does the same to the others.
private void saveURLToImage(string url)
{
if (!string.IsNullOrEmpty(url))
{
string content = "";
System.Net.WebRequest webRequest = WebRequest.Create(url);
System.Net.WebResponse webResponse = webRequest.GetResponse();
System.IO.StreamReader sr = new StreamReader(webResponse.GetResponseStream(), System.Text.Encoding.GetEncoding("UTF-8"));
content = sr.ReadToEnd();
//save to file
byte[] b = Convert.FromBase64String(content);
System.IO.MemoryStream ms = new System.IO.MemoryStream(b);
System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
img.Save(#"c:\pic.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
img.Dispose();
ms.Close();
}
}

Unless I'm misunderstanding you, this is impossible.
You cannot instruct the user's browser to take a screenshot (this would be a security risk … and has few uses cases anyway).
You cannot load the page you want a screenshot of yourself (with server side code) because you don't have the credentials needed to access it.

server side
Take a screenshot of a webpage with JavaScript?
javascript
http://html2canvas.hertzen.com/