App.set is not a function

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Answer:

The error “app.set is not a function” can occur when trying to use the set method on an undefined or incorrectly defined object.

In Express.js, the app.set method is used to set various configuration settings for your application.

Reasons for the error:

  1. The app object is not properly defined.
  2. A different object is being used instead of the app object.
  3. The Express.js framework is not properly set up.

Solution:

To resolve the “app.set is not a function” error, you need to make sure that you have properly initialized the Express.js application object.

Here is an example of how to correctly create and set up an Express.js application:

// Require the necessary modules
const express = require('express');

// Create an instance of Express application
const app = express();

// Set up necessary configurations
app.set('view engine', 'ejs'); // Example setting the view engine to EJS
app.set('port', 3000); // Example setting the port number

// Define your routes and middleware

// Start the server
app.listen(app.get('port'), () => {
  console.log('Server started on port ' + app.get('port'));
});

In the above example, we first require the Express module and create an instance of the app object using express() function.

Then we use the app.set method to configure the application, such as setting the view engine to EJS (app.set('view engine', 'ejs')) and the port number (app.set('port', 3000)).

After setting up the necessary configurations, you can continue defining your routes and middleware.

Finally, the app.listen method is used to start the server and listen on the specified port.

Make sure that you have the necessary dependencies installed and that you are running the correct file or script where the Express.js application is defined.

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