Using Functions in Flows

When building a flow you can use the Function step to perform advanced formatting on data using JavaScript.

For example:

• extracting JSON from an HTTP response and converting it to a numbered list string that is inserted into a message
• changing dates into a preferred format
• formatting numbers to include decimals
• compiling a payment URL with various parameters

Input

Function steps have a required input field that expects a JSON object.

If you want to pass the response from an HTTP request step into a function as input you can do so by putting {{session.requestName.body}} into the input field.

Tips for writing functions

The UI for editing functions is currently very minimal and it can be a bit tedious to continuously publish a new flow just to test if your function iteration is working.

We plan to introduce improvements to improve the code editing and testing experience but for now we recommend using a service like Stackblitz to write and test your functions first and then copy them over into the Function step code block.

For example:

// Test data
const data = {
    accounts: [
        "67388217",
        "92037742",
        "23099300"
    ] 
}

// Function code
function main(input) {
  var accountStrings = [];
  
  for(var i = 0; i < input.accounts.length; i++) {
    var accountNumber = input.accounts[i];
    var accountString = `${i + 1}. ${accountNumber}`;
    accountStrings.push(accountString);
  }
  return  accountStrings.join("\n")
}

// Test function call
const result = main(data)
console.log(result)

// 1. 67388217
// 2. 92037742
// 3. 23099300

Also, we've found it helpful to use a tool like ChatGPT to write an initial function for you from a prompt but be careful to test and verify that it has given you a working function before inserting it into your flow.

Output

To access the output returned from your function you can use {{session.functionName.output}} anywhere in your flow.

In a lot of cases it's best to return a fully formatted string of the text you want to display (e.g. an numbered list of n options) and then insert that output into a message.

If your function returns an object with multiple properties that you want to reference you will need to use the Set step to assign each of these to a custom session property. You cannot reference them using dot notation. For example, it is not possible to insert {{session.functionName.output.foo}} into a message.

Caveats

• Functions cannot make network calls to the outside internet.

Planned improvements

We plan to introduce the following improvements in the near future:

• Larger code editing window
• Function testing within the UI
• A flow simulator so that you can test your flows from within the editing UI
• The ability to prompt AI to write a function for you