Enable CORS on a token generation function.

[Testman]

I'm trying to use Twilio Functions instead of a current Express.JS server that we use to generate tokens. I've created the following function in Twilio functions:

exports.handler = function(context, event, callback) {

  const ClientCapability = require('twilio').jwt.ClientCapability;

let identity = "sampleIdentity";

  const capability = new ClientCapability({

           accountSid: context.ACCOUNT_SID,

           authToken: context.AUTH_TOKEN

        });

  capability.addScope(new ClientCapability.IncomingClientScope(identity));

  capability.addScope(new ClientCapability.OutgoingClientScope({

           applicationSid: context.TWILIO_TWIML_APP_SID

        }));

  callback(null, {identity: identity, token: capability.toJwt()});

};

But I'm receiving the error 

No 'Access-Control-Allow-Origin' header is present on the requested resource.

I know that's because I haven't set the Access-Control-Allow-Origin to a specific domain / '*' but I am having trouble figuring out how to do that on a plain node.js function like this. I know how to set this in Express, but I can't find how to do it for this. Has anyone else done this?

[Martin Amps]

Hi!

Thanks for trying out Functions. You can absolutely set CORS headers, there's an example from the docs @ https://www.twilio.com/docs/api/runtime/functions/faq#how-do-i-send-cors-headers

exports.handler = function(context, event, callback) {  const response = new Twilio.Response();  response.appendHeader('Access-Control-Allow-Origin', 'example.com');  response.appendHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');  response.appendHeader('Access-Control-Allow-Headers', 'Content-Type');  callback(null, response);};

Let us know if you have any further questions!

Martin

[Testman]

Using this code, I can make my code no longer produce a CORS error, but I how to I return the token I generated and assign it to a local variable?<br>

My Client-Side code:

     $('#new-twilio').click(function(){
        var toNum = this.value;
        if(token == undefined) {
            $.getJSON('https://my-twilio-function/endpoint').done(function(data){
                token = data.token;
                Twilio.Device.setup(token, {debug: true});
                Twilio.Device.ready(function(device){
                    Twilio.Device.connect({"PhoneNumber": toNum});  
                });
            }).fail(function(error){
                alert("Failure!");
                alert(JSON.stringify(error));
            });
        } else {
            Twilio.Device.connect({"PhoneNumber": toNum});
        }
    });

my function code now:

exports.handler = function(context, event, callback) {

const client = context.getTwilioClient();

  const ClientCapability = require('twilio').jwt.ClientCapability;

const response = new Twilio.Response();

  response.appendHeader('Access-Control-Allow-Origin', '*');

  response.appendHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');

  response.appendHeader('Access-Control-Allow-Headers', 'Content-Type');

  let identity = "sampleIdentity";

  const capability = new ClientCapability({

      accountSid: context.ACCOUNT_SID,

      authToken: context.AUTH_TOKEN

    });

  capability.addScope(new ClientCapability.IncomingClientScope(identity));

  capability.addScope(new ClientCapability.OutgoingClientScope({

      applicationSid: context.TWILIO_TWIML_APP_SID

    }));

  console.log(capability.toJwt());

  callback(null, response, {identity: identity, token: capability.toJwt()});

};

I tried placing the token in the response headers, but I'm not able to assign it in the JQuery function.

Thanks so much for the help!

[Martin Amps]

Close!

Instead of the json being in the 3rd arg, make it

callback(null, response);

and add something like:

response.setBody({identity: identity, token: capability.toJwt()});
response.appendHeader('Content-Type', 'application/json');

that should work for ya! Some relevant docs are here: https://www.twilio.com/docs/api/runtime/functions/environment

[Testman]

Thank you! It's working great now.

[Martin Amps]

Great news!