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 express module:

1. You can visit the link to Install express module. You can install this package by using this command.

   npm install express

2. After installing the express module, you can check your express version in command prompt using the command.

   npm version express

3. 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();

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

console.log(app.locals.email);

Steps to run the program:

1. The project structure will look like this:
   
2. Make sure you have installed express module using the following command:

   npm install express

3. Run index.js file using below command:

   node index.js

   Output:

   demo@gmail.com
   

Example 2: Filename: index.js

var express = require('express');
var 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);

Run index.js file using 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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