How Can I Pass Data From Flask To Javascript In A Template

Flask is a popular web framework for Python that allows you to build web applications and APIs easily. One common requirement in web development is passing data from the backend, in this case, Flask, to the frontend, which is usually handled by JavaScript in a template.

In Flask, you can pass data from the backend to a template using the `render_template` method. This method allows you to render a template and pass context data to it. To pass data from Flask to JavaScript in a template, you can use the `render_template` method with a dictionary containing the data you want to pass.

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def index():
    data = {'name': 'John Doe', 'age': 30}
    return render_template('index.html', data=data)

In the above example, we are passing a dictionary called `data` to the `index.html` template. Now, let's see how you can access this data in the template using JavaScript.

In your HTML template file, you can access the passed data using Jinja templating syntax and then use JavaScript to manipulate or display this data as needed. Here's an example of how you can access the `data` dictionary in a JavaScript script tag inside your template:

<title>Passing Data from Flask to JavaScript</title>


    <h1>Hello, {{ data.name }}!</h1>

    
        let name = "{{ data.name }}";
        let age = {{ data.age }};
        
        console.log(name);
        console.log(age);

In this template, we are accessing the `name` and `age` variables from the `data` dictionary using the Jinja templating syntax `{{ data.name }}` and `{{ data.age }}`. These values are then assigned to JavaScript variables, which can be used for further processing or displaying on the frontend.

By combining Flask's `render_template` method with Jinja templating and JavaScript, you can seamlessly pass data from your backend to the frontend in your web application. This capability allows you to create dynamic and interactive web pages that respond to changes in data fetched from the server.

In conclusion, passing data from Flask to JavaScript in a template involves leveraging Flask's `render_template` method, Jinja templating syntax, and JavaScript scripting in your HTML templates. By following the examples and techniques outlined in this article, you can effectively pass data between your Flask backend and JavaScript frontend to create engaging web applications.