***

id: ca4c2ae8-2768-4941-b126-aae71c9e1e31
title: Variables
slug: /guides/variables
max-toc-depth: 3
----------------

## Introduction

Variables allow you to create a dynamic Call Flow that responds to user input and other outside information.

While the [Set Variables](/docs/call-flow-builder/reference/set-variables) node allows you to manually create your own variables at any time,
you can also use variables from [Request](/docs/call-flow-builder/reference/request) nodes or even get variables from the inbound call.
All variables must be in the following format to signal to the Call Flow Builder that it should process a variable: `%{<variable>}`.

### Inbound Call Variables

The following variables exist for all inbound calls. At this time, the direction is always inbound,
but the other values are very useful and can be referenced throughout the whole Flow.

<ParamField path="%{call.from}" type="string" toc={true}>
  The phone number of the caller.
</ParamField>

<ParamField path="%{call.to}" type="string" toc={true}>
  The phone number the call was made to.
</ParamField>

<ParamField path="%{call.direction}" type="string" toc={true}>
  The direction of the call.
</ParamField>

<ParamField path="%{call.call_id}" type="string" toc={true}>
  The unique identifier for the call.
</ParamField>

<ParamField path="%{call.state}" type="string" toc={true}>
  The state of the call.
</ParamField>

<ParamField path="%{call.type}" type="string" toc={true}>
  The type of call.
</ParamField>

<br />

#### Variable Example

<Frame caption="Pass the caller phone number using a variable.">
  ![Using a phone number as a variable in a Call Flow.](https://files.buildwithfern.com/signalwire.docs.buildwithfern.com/docs/337c0a6e04643f5b56c53a3db66cdc38dd133b7851d8f0d6f36ab1634b67b41b/assets/images/call-flow/to-variable.webp)
</Frame>

***

### Request Variables

Variables that you get from a [Request](/docs/call-flow-builder/reference/request) node can be accessed using `%{request_response.<object_field>}`.
For example, if we send a GET request to [timeapi.io](https://www.timeapi.io/swagger/index.html), the response we'll receive will look like this:

```
{
  "year": 2023,
  "month": 7,
  "day": 27,
  "hour": 16,
  "minute": 9,
  "seconds": 9,
  "milliSeconds": 640,
  "dateTime": "2023-07-27T16:09:09.640945",
  "date": "07/27/2023",
  "time": "16:09",
  "timeZone": "America/Chicago",
  "dayOfWeek": "Thursday",
  "dstActive": true
}
```

To reference the `hour`, `date`, and `dayOfWeek` from this response as variables in the Call Flow, we would format the variables like this:

`%{request_response.hour}`
`%{request_response.date}`
`%{request_response.dayOfWeek}`

Please note that response values that are strings will need special formatting to be used with conditional expressions or JavaScript operators.
Use the format `%{vars.request_response.<object_field>'}` to use the value of the string.

In the example above, the response parameter `dayOfWeek` has a string value of `Thursday`.
The following condition will only be met when the day of the week is Thursday:

`%{vars.request_response.dayOfWeek == 'Thursday'}`

You can also use `slice()` to remove everything from the string after the third character to give you a shortened day of the week (Fri, Sat, Mon):

Key: `short_day`
Value: `%{vars.request_response.dayOfWeek.slice(0,3)}`

### Variables with JavaScript Operators

You can use variables along with [standard Javascript operators](https://www.w3schools.com/js/default.asp).
This can be useful if you need to alter a variable or pass a condition that matches an expression.

For example, you can use the [`slice()` method](https://www.w3schools.com/jsref/jsref_slice_string.asp)
to remove everything from the `%{call.from}` variable except for the area code of an inbound caller.
Within a [Set Variables](/docs/call-flow-builder/reference/set-variables) node, you can set the following:

**Key:** `area_code`

**Value:** `%{call.from.slice(2,5)}`

You can even combine this with a [Conditions](/docs/call-flow-builder/reference/conditions) node as in the example below.
Condition 1 uses the OR operator to check if the area code is 321 or 407.

If either of those is true, the call is forwarded to +15552223333.
A second condition in the same node checks for a 419 area code and forwards the call to +15553334444.

Condition 1: `%{area_code}==321||%{area_code}==407`
Condition 2: `%{area_code}==419`

<Frame caption="Use the `slice()` method to alter a variable.">
  ![Using slice to alter a variable.](https://files.buildwithfern.com/signalwire.docs.buildwithfern.com/docs/19a49f45f928babba9747607274387c6c11ba1ae7f672f87f59700043cbd30be/assets/images/call-flow/slice-variable.webp)
</Frame>