Passing JavaScript variable to Python Flask

JavaScript and Python Flask are two popular programming languages that are often used together to create web applications. In this article, we will explore how to pass a JavaScript variable to a Python Flask backend.

Using AJAX for communication

One of the most common ways to pass a JavaScript variable to a Python Flask backend is by using AJAX (Asynchronous JavaScript and XML). With AJAX, you can make asynchronous requests to the server and update the page without a full page reload.

Example

Let’s take a look at an example of how to pass a JavaScript variable to a Python Flask backend using AJAX.

    
      // JavaScript code
      var data = {
        name: "John Doe",
        age: 30
      };

      $.ajax({
        type: "POST",
        url: "/process_data",
        data: JSON.stringify(data),
        contentType: 'application/json',
        success: function(response) {
          console.log(response);
        }
      });
    
  

In the above example, we are sending a JSON object containing name and age to the “/process_data” endpoint in our Python Flask backend using an AJAX POST request.

Handling the request in Python Flask

Once the AJAX request is sent, we need to handle the incoming data in our Python Flask backend. Here’s an example of how to do this:

    
      # Python Flask code
      from flask import Flask, request

      app = Flask(__name__)

      @app.route('/process_data', methods=['POST'])
      def process_data():
          data = request.get_json()
          name = data['name']
          age = data['age']
          # Do something with the data
          return "Data processed successfully"

      if __name__ == '__main__':
          app.run()
    
  

In the Python Flask code, we define a route “/process_data” that accepts POST requests. We then use the request.get_json() method to retrieve the JSON data sent from the JavaScript frontend and process it as needed.

Conclusion

Passing a JavaScript variable to a Python Flask backend is a common task when building web applications. With the help of AJAX and Python Flask, you can easily communicate between the frontend and backend and build powerful web applications.