How to Run JavaScript in Power Automate

Introduction

Running inline JavaScript can be a powerful way to extend your workflows. This guide will walk you through the steps to set this up in Power Automate via a custom connector for an Azure Function.

Step 1: Create an Azure Function

1. Log in to the Azure Portal: Go to Azure Portal.
2. Create a new Function App: Navigate to “Create a resource” > “Compute” > “Function App”.
3. Configure your Function App:
   • Subscription: Choose your subscription.
   • Resource Group: Create a new resource group or select an existing one.
   • Function App name: Enter a unique name.
   • Runtime stack: Select “Node.js”.
   • Region: Choose a region close to you.
4. Review and create: Review your settings and click “Create”.

Step 2: Develop the Azure Function

1. Navigate to your Function App: Once created, go to your Function App.
2. Create a new function: Click on “Functions” > “Add” > “HTTP trigger”.
3. Configure the function:
   • Name: Give your function a name.
   • Authorization level: Choose “Function”.
4. Write your JavaScript code: Replace the default code with this:

module.exports = async function (context, req) {
  context.res = {
    body: {},
    headers: {
      "content-type": "application/json"
    }
  };

  if (!req.body || typeof req.body !== "string") {
    context.res.status = 400;
    context.res.body = { error: "Invalid input" };
    return;
  }

  try {
    const result = new Function(req.body)();
    context.res.body = { result };
  } catch (e) {
    context.res.status = 400;
    context.res.body = { error: e.message };
  }
};

5. Save and test: Save your function and test it using the “Test/Run” feature.

Step 3: Create a Custom Connector in Power Automate

1. Log in to Power Automate: Go to Power Automate.
2. Create a new custom connector:
   • Navigate to “Data” > “Custom connectors” > “New custom connector” > “Create from blank”.
3. Configure the custom connector:
   • General: Enter a name and description.
   • Scheme: HTTPS
   • Host: Enter the base URL of your API Management instance.
   • Security: API key

• Definition: New Action

  • Summary: Evaluate
  • Description: Evaluates inline JavaScript passed as a string to the request body
  • Visibility: important

• Request: Import from sample

  • Verb: POST
  • URL: Your function URL
  • Import

• Response: default > Import from sample
  • Body: { "result": null }

• Swagger editor: paste the following into the parameters section of the /Evaluate path:

parameters:
  - name: script
    in: body
    required: true
    schema:
      type: string

• The completed swagger should look as follows:

swagger: "2.0"
info:
  title: Evaulate
  description: Connects to an Azure Function
  version: "1.0"
host: <your base url>
basePath: /api
schemes:
  - https
consumes: []
produces: []
paths:
  /Evaulate:
    post:
      responses:
        default:
          description: default
          schema:
            type: object
            properties:
              result:
                type: string
                description: result
                title: result
      summary: Evaluate
      description: Evaluates inline JavaScript passed as a string to the request body
      operationId: Evaluate
      x-ms-visibility: important
      parameters:
        - name: script
          in: body
          required: true
          schema:
            type: string
definitions: {}
parameters: {}
responses: {}
securityDefinitions:
  Key:
    type: apiKey
    in: header
    name: x-functions-key
security:
  - Key: []
tags: []

1. Create Connector
2. Create a Connection: Add New Connection > Key > Create

3. Test the connector: script > return 2+ 2 > Test operation

Step 4: Use the Custom Connector in a Flow

1. Create a new flow: Go to “My flows” > “New flow”.
2. Add a trigger: Choose a trigger to start your flow.
3. Add an action: Search for your custom connector and add the action you defined.
4. Configure the action: Enter any required parameters.
5. Save and test the flow: Save your flow and test it to ensure it runs correctly.

By following these steps, you can run JavaScript via a custom connector for an Azure Function in Power Automate, enabling you to create powerful and flexible workflows.