# Add Delay

> \[!CAUTION]
>
> Functions are subject to a [10-second execution limit](/docs/serverless/functions-assets/functions/request-flow) before being terminated. Keep this limit in mind when evaluating if this method suits your use case.

Adding a delay to your Function's response is useful in certain use cases, particularly when it comes to interacting with [Twilio Studio](/docs/studio). One such case is if you are creating a chatbot and want longer, more realistic pauses between responses. Or perhaps you are making an HTTP request in a Studio [Flow](/docs/studio/rest-api/v2/flow) and want to add a delay to the retry loop on failure.

In all of these situations, the ability to add a delay is incredibly helpful. While Studio does not provide a native "Delay" widget, you can combine the [Run Function widget](/docs/serverless/functions-assets/quickstart/run-function-studio-widget) with a Function that has a delayed response to emulate such behavior.

Below are some examples of what such a Function may look like. Before getting deeper into the examples, first, create a Service and Function so that you have a place to write and test your Function code.

## Create and host a Function

Before you run any of the examples on this page, create a Function and paste the example code into it. You can create a Function in the Twilio Console or by using the [Serverless Toolkit](/docs/labs/serverless-toolkit).

## Console

If you prefer a UI-driven approach, complete these steps in the Twilio Console:

1. Log in to the [Twilio Console](https://1console.twilio.com) and navigate to **Develop > Functions & Assets**. If you're using the *legacy* Console, open the [**Functions** tab](https://www.twilio.com/console/functions/overview).
2. Functions are contained within **Services**. Click **[Create Service](https://www.twilio.com/console/functions/overview/services)** to create a new **[Service](/docs/serverless/functions-assets/functions/create-service)**.
3. Click **Add +** and select **Add Function** from the dropdown.
4. The Console creates a new [protected](/docs/serverless/functions-assets/visibility) Function that you can rename. The filename becomes the URL path of the Function.
5. Copy one of the example code snippets from this page and paste the code into your newly created Function. You can switch examples by using the dropdown menu in the code rail.
6. Click **Save**.
7. Click **Deploy All** to build and deploy the Function. After deployment, you can access your Function at `https://<service-name>-<random-characters>-<optional-domain-suffix>.twil.io/<function-path>`\
   For example: `test-function-3548.twil.io/hello-world`.

## Serverless Toolkit

The [Serverless Toolkit](/docs/labs/serverless-toolkit) lets you develop locally, deploy projects, and perform other tasks through the [Twilio CLI](/docs/twilio-cli/quickstart).

1. From the CLI, run `twilio serverless:init <YOUR-SERVICE-NAME> --empty` to bootstrap your local environment.
2. Go to your new project directory using `cd <YOUR-SERVICE-NAME>`.
3. In the `/functions` directory, create a JavaScript file whose name reflects the purpose of the Function. For example, `sms-reply.protected.js` for a [protected](/docs/serverless/functions-assets/visibility) Function intended to handle incoming SMS.
4. Add the code example of your choice to the file and save it. Note that a Function can only export a single handler. You need to create separate files to run or deploy multiple examples at once.

After you save the Function code, you can test it locally (and optionally tunnel requests to it using a tool like [ngrok](https://ngrok.com/)), or deploy it.

### Run your Function in local development

Run `twilio serverless:start` from your CLI to start the project locally. The Function(s) in your project are accessible from `http://localhost:3000/sms-reply`

* If you want to test a Function as a [Twilio webhook](/docs/usage/webhooks/getting-started-twilio-webhooks), run: `twilio phone-numbers:update <your Twilio phone number> --sms-url "http://localhost:3000/sms-reply"`\
  This automatically generates 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-url` flag instead to test with [Twilio Voice](/docs/voice).
* If your code does *not* connect to Twilio Voice or Messages as a webhook, start your dev server and start an ngrok tunnel in the same command with the `ngrok` flag. 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 deploys your Function(s) to Twilio under a development Environment by default, where they can be accessed from:

`https://<service-name>-<random-characters>-dev.twil.io/<function-path>`

For example: `https://incoming-sms-examples-3421-dev.twil.io/sms-reply`

You can now invoke your Function with HTTP requests, configure it as the [webhook](/docs/usage/webhooks/getting-started-twilio-webhooks) for a Twilio phone number, call it from a Twilio Studio [**Run Function** Widget](/docs/studio/widget-library/run-function), and more.

## Create a Delay Function

The act of delaying a Function's response is mostly just a matter of using a built-in method, such as `setTimeout`, to delay the act of calling the `callback` method and signaling that the Function has completed. If this Function were to be called by a Run Function widget, the Studio Flow containing that call would be delayed until this Function returns a response.

It's also quite possible to provide the value for `delay`, by defining a value (or [dynamic variable](/docs/studio/user-guide/liquid-template-language)) under the **Function Parameters** config for the [Run Function Widget](/docs/studio/widget-library/run-function) that calls this Function.

To provide a more `async`/`await` friendly syntax in your Functions, this example demonstrates how to write a `sleep` helper method that wraps `setTimeout` in a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).

If your Function has no other actions to execute or if you don't see the need for Promises in this case, the next example demonstrates the same functionality, but without the `async`/`await` abstraction.

```js title="Delayed response Function"
// Helper function for quickly adding await-able "pauses" to JavaScript
const sleep = (delay) => new Promise((resolve) => setTimeout(resolve, delay));

exports.handler = async (context, event, callback) => {
  // A custom delay value could be passed to the Function, either via
  // request parameters or by the Run Function Widget
  // Default to a 5-second delay
  const delay = event.delay || 5000;
  // Pause Function for the specified number of ms
  await sleep(delay);
  // Once the delay has passed, return a success message, TwiML, or
  // any other content to whatever invoked this Function.
  return callback(null, `Timer up: ${delay}ms`);
};
```

```js title="Delayed response Function" description="Without async/await or Promises"
exports.handler = (context, event, callback) => {
  // A custom delay value could be passed to the Function, either via
  // request parameters or by the Run Function Widget
  // Default to a 5-second delay
  const delay = event.delay || 5000;
  // Set a timer for the specified number of ms. Once the delay has passed,
  // return a success message, TwiML, or any other content to whatever
  // invoked this Function.
  setTimeout(() => callback(null, `Timer Up: ${delay}ms`), delay);
};
```

## Refactoring the sleep method

The `sleep` method that we created for the previous example is also a great example of a method that could be used across a number of Functions in your Service. In Functions, it's best practice to store shared JavaScript methods such as these in [Private Functions](/docs/serverless/functions-assets/visibility), and import them into the various Functions that will make use of them.

To see this in action, first create a new Function named `utils`, and set its privacy level to Private. Paste in the following code, which exports the `sleep` helper from before.

```js title="Private shared utilities Function" description="An example of a Private Function which hosts shared methods across Functions"
// Helper function for quickly adding await-able "pauses" to JavaScript
exports.sleep = (delay) => new Promise((resolve) => setTimeout(resolve, delay));
```

Next, open your existing Delay Function, remove the inline declaration of sleep, and add the highlighted line of code. Save and deploy all changes.

This is a demonstration of using the [Runtime.getFunctions](/docs/serverless/functions-assets/client#getfunctions) helper to import shared code from a private Function, which can help to [DRY](https://en.wikipedia.org/wiki/Don%27t_repeat_yourself) up your Functions code.

```js title="Delayed response Function" description="A delayed Function that leverages a utility method instead of defining it inline"
// !mark(4)
exports.handler = async (context, event, callback) => {
  // You can import shared code from a Private Function
  // using the Runtime.getFunctions() helper + require
  const { sleep } = require(Runtime.getFunctions().utils.path);
  // A custom delay value could be passed to the Function, either via
  // request parameters or by the Run Function Widget
  // Default to a 5-second delay
  const delay = event.delay || 5000;
  // Pause Function for the specified number of ms
  await sleep(delay || 5000);
  // Once the delay has passed, return a success message, TwiML, or
  // any other content to whatever invoked this Function.
  return callback(null, `Timer up: ${delay}ms`);
};
```