Express.js Mount Event
The mount event is fired on a sub-app when it is mounted on a parent app and the parent app is basically passed to the callback function.
Syntax:
app.on('mount', callback(parent))
Parameter: It is an event named ‘mount’, and callback function is called when this event is called.
Return Value: Since its an event so it doesn’t have any return value.
Installation of express module:
- You can visit the link to Install express module. You can install this package by using this command.
npm install express
- After installing the express module, you can check your express version in command prompt using the command.
npm version express
- After that, you can just create a folder and add a file for example, index.js. To run this file you need to run the following command.
node index.js
Example 1: Filename: index.js
var express = require( 'express' ); var app = express(); // The main app var admin = express(); var PORT = 3000; admin.on( 'mount' , function (parent) { console.log( 'Admin Mounted' ); }); admin.get( '/' , function (req, res) { res.send( 'Admin Homepage' ); }); app.use( '/admin' , admin); app.listen(PORT, function (err){ if (err) console.log(err); console.log( "Server listening on PORT" , PORT); }); |
Steps to run the program:
- The project structure will look like this:
- Make sure you have installed express module using the following command:
npm install express
- Run index.js file using below command:
node index.js
Output:
Admin Mounted Server listening on PORT 3000
- Now open your browser and go to http://localhost:3000/admin, now you can see the following output on your screen:
Admin Homepage
Example 2:
Filename: index.js
var express = require( 'express' ); var app = express(); // The main app var student = express(); var teacher = express(); var PORT = 3000; // Multiple mounting teacher.on( 'mount' , function (parent) { console.log( 'Teacher Mounted' ); }); student.on( 'mount' , function (parent) { console.log( 'Student Mounted' ); }); app.use( '/student' , student); app.use( '/teacher' , teacher); app.listen(PORT, function (err){ if (err) console.log(err); console.log( "Server listening on PORT" , PORT); }); |
Run index.js file using below command:
node index.js
Output: Now open your browser and make GET request to http://localhost:3000, now you can see the following output on your console:
Student Mounted Teacher Mounted Server listening on PORT 3000
Reference: https://expressjs.com/en/4x/api.html#app.onmount
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