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How to build Form builder backend with Lovable?

Learn how to build a robust form builder backend using Lovable. Our step-by-step guide offers expert tips and best practices for seamless integration.

Matt Graham, CEO of Rapid Developers

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How to build Form builder backend with Lovable?

 
Prerequisites
 

  • A Lovable account with access to the built-in code editor.
  • Basic understanding of JavaScript and backend concepts.
  • An existing Lovable project where you can add new files and code.

 
Creating a New Lovable Project or Using an Existing One
 

  • Log into your Lovable account and either create a new project or open an existing one where you plan to build your form builder backend.
  • Make sure you have access to the file management section where you can create, edit, and manage source files.

 
Adding Dependencies Without a Terminal
 

  • Since Lovable does not have a terminal, you must include any third-party libraries manually by referencing them in your code.
  • For this example, we will use Express for setting up the server and body-parser to handle JSON payloads. Include these dependencies at the top of your backend code file by using a script tag or, if Lovable supports Node.js modules directly in the code editor, by requiring them. Add the following snippet to install dependencies:
    • 
      // Begin dependency setup
      const express = require('express');
      const bodyParser = require('body-parser');
      // End dependency setup
            
  • If Lovable requires you to mimic dependency installation (for example, via an online import URL), consult Lovable’s documentation for how to include external libraries. Often, you can use a CDN link in an HTML file if needed.

 
Creating the Backend File
 

  • Create a new file in your Lovable project called backend.js. This file will contain all the backend logic for your form builder.
  • Place the dependency setup snippet at the very top of this file, as shown in the previous step.

 
Setting Up Your Express Server
 

  • After initializing the dependencies in backend.js, set up your Express server. Add the following code snippet immediately after the dependency setup to configure middleware and start the server:
    • 
      const app = express();
      
      

      // Configure middleware to parse JSON data in requests
      app.use(bodyParser.json());

      // A simple route to ensure the server is running
      app.get('/', (req, res) => {
      res.send('Welcome to the Form Builder Backend!');
      });



 
Building the Form Submission Endpoint
 

  • Create an endpoint that will accept form submissions from the frontend. In the same backend.js file, add the following code after setting up the server:
    • 
      app.post('/submit-form', (req, res) => {
        // Extract the form data from the request body
        const formData = req.body;
        
      

      // Process the form data (e.g., store it in a database or log it)
      console.log('Received form data:', formData);

      // Respond to the client with a success message
      res.status(200).send({ message: 'Form submitted successfully.' });
      });



 
Starting the Server
 

  • At the bottom of the backend.js file, add the snippet to start the server. This allows the server to listen on a specified port:
    • 
      const PORT = 3000; // or any port of your choice
      app.listen(PORT, () => {
        console.log(`Form Builder Backend is running on port ${PORT}`);
      });
            
  • Make sure this code is included in backend.js so that when your project runs, Lovable will execute this file as your backend service.

 
Connecting the Frontend Form to the Backend
 

  • In your Lovable project, locate the file that contains your frontend form (for example, index.html or app.js if you have a separate file).
  • Ensure that when a user submits the form, a POST request is sent to the /submit-form endpoint. Add this sample AJAX snippet in your frontend code to achieve this:
    • 
      fetch('/submit-form', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          // Replace with your actual form field names and values
          name: document.getElementById('name').value,
          email: document.getElementById('email').value,
          message: document.getElementById('message').value
        })
      })
      .then(response => response.json())
      .then(data => {
        console.log('Success:', data);
      })
      .catch((error) => {
        console.error('Error:', error);
      });
            
  • This code can be placed in a relevant JavaScript file (like app.js) or within a <script> tag on your form page.

 
Testing Your Form Builder Backend
 

  • After completing the setup, run your Lovable project to start the server.
  • Open your form page in a browser, fill out the form, and submit it. Check Lovable’s log console or the browser console to see if the form data is logged as expected.
  • If everything works correctly, the backend will respond with a success message and handle the form data as intended.

 
Deploying and Sharing Your Project
 

  • Each time you make changes to your code, save the file in Lovable and refresh your preview to see the updates.
  • Use Lovable’s built-in sharing options to distribute your project’s URL with others for testing or feedback.

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How to Create and Fetch Forms with Lovable’s Express Backend


"use strict";
const express = require('express');
const router = express.Router();
const LovableFormModel = require('./models/LovableForm');
const validateFormSchema = require('./validators/formSchemaValidator');

router.post('/createForm', async (req, res, next) => {
  try {
    const schema = req.body.schema;
    const validatedSchema = await validateFormSchema(schema);
    const formConfig = {
      title: req.body.title,
      description: req.body.description,
      schema: validatedSchema,
      createdAt: new Date()
    };
    const newForm = new LovableFormModel(formConfig);
    const savedForm = await newForm.save();
    res.status(201).json({ id: savedForm.\_id, message: "Form created successfully" });
  } catch (error) {
    next(error);
  }
});

router.get('/form/:id', async (req, res, next) => {
  try {
    const form = await LovableFormModel.findById(req.params.id);
    if (!form) return res.status(404).json({ message: "Form not found" });
    res.status(200).json(form);
  } catch (error) {
    next(error);
  }
});

module.exports = router;

How to prefill your Lovable form using external API data


"use strict";
const express = require('express');
const axios = require('axios');
const router = express.Router();
const LovableFormModel = require('./models/LovableForm');

router.post('/prefillForm', async (req, res, next) => {
  try {
    const { formId, externalApiUrl } = req.body;
    const form = await LovableFormModel.findById(formId);
    if (!form) {
      return res.status(404).json({ message: 'Form not found' });
    }
    const response = await axios.get(externalApiUrl);
    const prefillData = response.data;

    form.schema.fields = form.schema.fields.map(field => {
      if (prefillData[field.name] !== undefined) {
        return { ...field, defaultValue: prefillData[field.name] };
      }
      return field;
    });

    const updatedForm = await form.save();
    res.status(200).json({ id: updatedForm.\_id, message: 'Form prefilled successfully' });
  } catch (error) {
    next(error);
  }
});

module.exports = router;

How to Duplicate a Form with Field Transformations in Your Lovable Backend


"use strict";
const express = require('express');
const router = express.Router();
const LovableFormModel = require('./models/LovableForm');

function transformField(field) {
  const newField = { ...field };
  if (field.type === 'text' && field.maxLength && field.maxLength > 100) {
    newField.type = 'textarea';
    newField.placeholder = "Enter detailed response here...";
  }
  if (field.type === 'number' && field.min !== undefined && field.max !== undefined) {
    newField.validation = {
      validator: value => value >= field.min && value <= field.max,
      message: `Value must be between ${field.min} and ${field.max}`
    };
  }
  return newField;
}

router.post('/duplicateForm', async (req, res, next) => {
  try {
    const { formId, newTitle } = req.body;
    const originalForm = await LovableFormModel.findById(formId);
    if (!originalForm) {
      return res.status(404).json({ message: 'Original form not found' });
    }
    const transformedFields = originalForm.schema.fields.map(transformField);
    const newFormConfig = {
      title: newTitle || `${originalForm.title} (Copy)`,
      description: originalForm.description,
      schema: { ...originalForm.schema, fields: transformedFields },
      createdAt: new Date(),
      sourceFormId: formId
    };
    const duplicatedForm = new LovableFormModel(newFormConfig);
    const savedForm = await duplicatedForm.save();
    res.status(201).json({
      id: savedForm.\_id,
      message: 'Form duplicated with transformations'
    });
  } catch (error) {
    next(error);
  }
});

module.exports = router;

Want to explore opportunities to work with us?

Connect with our team to unlock the full potential of no-code solutions with a no-commitment consultation!

Book a Free Consultation
Matt Graham, CEO of Rapid Developers

Book a call with an Expert

Starting a new venture? Need to upgrade your web app? RapidDev builds application with your growth in mind.

Book a free No-Code consultation

Best Practices for Building a Form builder backend with AI Code Generators

 
Introduction to Form Builder Backend with AI Code Generators
 

Developing a form builder backend powered by AI code generators involves creating a system that accepts user input, processes complex form configurations and then uses AI-driven components to generate the corresponding backend code dynamically. This guide provides a detailed walkthrough suitable for non-tech users, explaining concepts, outlining best practices, and offering clear code examples.

 
Prerequisites
 

  • A basic understanding of web applications and server-side processing.
  • Access to a development environment with Node.js, Python, or any server-side programming language.
  • Familiarity with RESTful API concepts and an idea of what artificial intelligence code generators do.
  • An AI code generation tool or API (for example, OpenAI Codex or similar).

 
Setting Up the Development Environment
 

  • Install your chosen programming language’s runtime (for example, Node.js for JavaScript or Python).
  • Set up your code editor (Visual Studio Code, Sublime, etc.).
  • Create a new project folder on your computer. Inside this folder, initialize your project. If using Node.js, run:
    
    npm init -y
        
  • For Python projects, consider setting up a virtual environment:
    
    python -m venv env
    source env/bin/activate  # on Windows use: env\Scripts\activate
        
  • Install necessary libraries (like Express for Node.js or Flask for Python) for API handling.

 
Designing Your Application Architecture
 

  • Define a clear separation of concerns in your project:
    • The API layer that receives and processes form configuration requests.
    • A business logic layer that handles processing, such as template management and AI-triggered code generation.
    • A persistence layer for storing form templates, user configurations, and generated code.
  • Plan API endpoints such as /createForm, /updateForm, /getForm, and /generateCode.
  • Sketch a high-level diagram to visually separate these components.

 
Building the API Endpoints
 

  • Create endpoints that allow users to define forms, update configurations, or retrieve generated backend code.
  • For example, in a Node.js Express project, you can define a basic endpoint as follows:
    
    const express = require('express');
    const app = express();
    app.use(express.json());
    
    

    app.post('/createForm', (req, res) => {
    const formConfig = req.body;
    // Process form configuration and store details
    res.json({ message: 'Form configuration received!' });
    });

    app.listen(3000, () => {
    console.log('Server running on port 3000');
    });



  • In a Python Flask project, an endpoint can be set up like this:

    from flask import Flask, request, jsonify

    app = Flask(name)

    @app.route('/createForm', methods=['POST'])
    def create_form():
    form_config = request.json
    # Process form configuration and store details
    return jsonify({'message': 'Form configuration received!'})

    if name == 'main':
    app.run(host='0.0.0.0', port=5000)


 
Integrating AI Code Generation
 

  • Identify the scenarios where AI can help generate backend code. For example, transforming form configurations into validation code or database models.
  • Integrate with an external AI code generator API:
    • Set up API authentication and keys securely within your project.
    • When a form configuration is submitted, call the AI API to generate code. Below is a conceptual example in Node.js:
      
      const axios = require('axios');
      
      

      async function generateCode(formConfig) {
      const response = await axios.post('https://api.aicodegenerator.com/generate', {
      prompt: 'Generate backend code for: ' + JSON.stringify(formConfig)
      }, {
      headers: { 'Authorization': 'Bearer YOUR_API_KEY' }
      });
      return response.data.code;
      }



    • For Python, you can use the requests library:

      import requests

      def generate_code(form_config):
      headers = {'Authorization': 'Bearer YOUR_API_KEY'}
      data = {'prompt': f'Generate backend code for: {form_config}'}
      response = requests.post('https://api.aicodegenerator.com/generate', json=data, headers=headers)
      return response.json().get('code')





  • Integrate the AI generation function with the /generateCode endpoint to provide users with the backend code automatically.

 
Implementing Data Storage and Management
 

  • Decide on a database system (SQL or NoSQL) to store form configurations and generated code snippets.
  • Set up your database and create tables/collections for storing forms. For example, a simple SQL table structure might be:
    
    CREATE TABLE forms (
      id SERIAL PRIMARY KEY,
      name VARCHAR(255) NOT NULL,
      configuration JSON NOT NULL,
      generated\_code TEXT,
      created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
    );
        

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