Express.js app.locals Property

The app.locals object has properties that are local variables within the application. These variables are local to the application and are very useful. 

Syntax:

app.locals

Parameter: No parameters. 

Return Value: Object 

Installation of the express module:

You can visit the link to Install the 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 the 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

Project Structure:

Example 1: Filename: index.js

javascript

const express = require('express');
const app = express();

// Setting single locals variable
app.locals.email = 'demo@gmail.com'

console.log(app.locals.email);

Steps to run the program:

Make sure you have installed the express module using the following command:

npm install express

Run the index.js file using the below command:

node index.js

Output:

demo@gmail.com

Example 2: Filename: index.js

javascript

const express = require('express');
const app = express();

// Setting multiple locals variable
app.locals.domain = 'www.sample.com'
app.locals.age = '24'
app.locals.company = 'ABC Ltd'

console.log(app.locals);

Steps to run the program:

Run the index.js file using the below command:

node index.js

Output:

[Object: null prototype] {
  settings: {
    'x-powered-by': true, 
    etag: 'weak',
    'etag fn': [Function: generateETag],
    env: 'development',
    'query parser': 'extended',
    'query parser fn': [Function: parseExtendedQueryString],
    'subdomain offset': 2,
    'trust proxy': false,
    'trust proxy fn': [Function: trustNone],
    view: [Function: View],
    views: 'C:\\Users\\Lenovo\\Downloads\\GFG 
      Reviewer Internship\\Program\\views',
    'jsonp callback name': 'callback'
  },
  domain: 'www.sample.com',
  age: '24',
  company: 'ABC Ltd'
}

Reference: https://expressjs.com/en/4x/api.html#app.locals

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