Enable CORS between Flex Plugins and Functions
This example uses headers and cookies, which are only accessible when your Function is running
1.2.0 or later. Consult the Runtime Handler guide to learn more about the latest version and how to update.
A common use case is to call Functions from a Flex Plugin to retrieve external data such as statistics. Sometimes, this results in Cross-Origin Resource Sharing (CORS) restrictions in production environments due to the different hostnames between the Flex Plugin and the Function being called.
Fortunately, CORS errors, in this context or other situations, can be addressed by leveraging the response headers of the Function to allow any Origin, as shown in the following example code.
Create and host a Function
In order to run any of the following examples, you will first need to create a Function into which you can paste the example code. You can create a Function using the Twilio Console or the Serverless Toolkit as explained below:
If you prefer a UI-driven approach, creating and deploying a Function can be done entirely using the Twilio Console and the following steps:
- Log in to the Twilio Console and navigate to the Functions tab. If you need an account, you can sign up for a free Twilio account here!
- Functions are contained within Services. Create a Service by clicking the Create Service button and providing a name such as test-function.
- Once you've been redirected to the new Service, click the Add + button and select Add Function from the dropdown.
- This will create a new Protected Function for you with the option to rename it. The name of the file will be path it is accessed from.
- Copy any one of the example code snippets from this page that you want to experiment with, and paste the code into your newly created Function. You can quickly switch examples by using the dropdown menu of the code rail.
- Click Save to save your Function's contents.
- Click Deploy All to build and deploy the Function. After a short delay, your Function will be accesible from:
The Serverless Toolkit enables you with local development, project deployment, and other functionality via the Twilio CLI. To get up and running with these examples using Serverless Toolkit, follow this process:
- From the CLI, run
twilio serverless:init <your-service-name> --emptyto bootstrap your local environment.
- Navigate into your new project directory using
- In the
sms-reply.protected.jsfor a Protected Function intended to handle incoming SMS.
- Populate the file using the code example of your choice and save.
Note A Function can only export a single handler. You will want to create separate files if you want to run and/or deploy multiple examples at once.
Once your Function(s) code is written and saved, you can test it either by running it locally (and optionally tunneling requests to it via a tool like ngrok), or by deploying the Function and executing against the deployed url(s).
Run your Function in local development
twilio serverless:start from your CLI to start the project locally. The Function(s) in your project will be accesible from
- If you want to test a Function as a Twilio webhook, run:
twilio phone-numbers:update <your Twilio phone number> --sms-url "http://localhost:3000/sms-reply"
This will automatically generate an ngrok tunnel from Twilio to your locally running Function, so you can start sending texts to it. You can apply the same process but with the
voice-urlflag instead if you want to test with Twilio Voice.
- If your code does not connect to Twilio Voice/Messages as a webhook, you can start your dev server and start an ngrok tunnel in the same command with the
ngrokflag. For example:
twilio serverless:start --ngrok=""
Deploy your Function
To deploy your Function and have access to live url(s), run
twilio serverless:deploy from your CLI. This will deploy your Function(s) to Twilio under a development environment by default, where they can be accessed from:
Your Function is now ready to be invoked by HTTP requests, set as the webhook of a Twilio phone number, invoked by a Twilio Studio Run Function Widget, and more!
If you want to learn more about Flex Plugins that would be invoking a Function in this way, check out this tutorial on calling a Function from a Flex Plugin.
Need some help?
We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd by visiting Twilio's Stack Overflow Collective or browsing the Twilio tag on Stack Overflow.