The Expression and Function actions perform custom data transformations within your workflows using JavaScript. Use the values of any context variables available within your workflow as inputs for your JavaScript expressions and functions with the syntax $.Steps.<step_name>.<variable>. You can also use _ to make use of Lodash in your data transformation actions with the same syntax. For example, to reference the HTTP request status variable (status) from the HTTP request step (Make_request), you’d use the following context variable:

$.Steps.Make_request.status

And to determine if an array returned by Array_function includes the name Bits, apply the _.includes Lodash function with the following syntax:

_.includes($.Steps.Array_function.data, "Bits")

The data returned by these actions can then be referenced in subsequent steps of the workflow.

Expression

Use expression actions for data transformations that can be accomplished in a single line of code, and do not require variable assignments or multiple standalone operations. For example:

[1, 2, 3].filter(x => x < 3)

To add an expression action:

• In a new workflow, click Add step and search for expression. Select the Expression action to add it to your workflow.
• In an existing workflow, click + and search for expression. Select the Expression action to add it to your workflow.

In an expression step, execution uses copies of all available variables. Mutating a variable within a step has no effect on the variable’s value outside of the step. To assign the result of an expression to a variable, see Set variables.

Function

The function action allows for variable assignments and data transformations requiring multiple expressions.

To add a function action:

• In a new workflow, click Add step and search for function. Select the Function action to add it to your workflow.
• In an existing workflow, click + and search for function. Select the Function action to add it to your workflow.

Write functions with AI

You can use Bits AI to help you write the JavaScript for a Function step. To use this feature, perform the following steps:

1. Add a Function step to your workflow.
2. Under General, in the Script field, click Write with Bits AI.
3. In the Describe your transformation script field, enter a description of what you want your script to do. Click the up arrow (↑) to submit your description.
4. Choose an option to Replace script, Insert in script, or Copy to clipboard.
5. Check the script and change it as necessary to fit your needs.

Test expressions and functions

See the test and debug page to learn how to test a workflow step.

Do you have questions or feedback? Join the #workflows channel on the Datadog Community Slack.