Steps to Installation the express module
Step 1: You can install this package by using this command.
npm install express
Step 2: After installing the express module, you can check your express version in the command prompt using the command.
npm version express
Step 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
Project Structure:
Example 1: Below is the code example of the express.json().
javascript
const express = require( 'express' ); const app = express(); const PORT = 3000; app.use(express.json()); app.post( '/' , function (req, res) { console.log(req.body.name) res.end(); }) app.listen(PORT, function (err) { if (err) console.log(err); console.log( "Server listening on PORT" , PORT); }); |
Steps to run the program:
Step 1:Make sure you have installed the express module using the following command:
npm install express
Step 2: Run the index.js file using the below command:
node index.js
Output: Now make a POST request to http://localhost:3000/ with header set to ‘content-type: application/json’ and body {“name”:”w3wiki”}, then you will see the following output on your console:
Server listening on PORT 3000
w3wiki
Example 2: Below is the code example of the express.json().
javascript
const express = require( 'express' ); const app = express(); const PORT = 3000; // Without this middleware // app.use(express.json()); app.post( '/' , function (req, res) { console.log(req.body.name) res.end(); }) app.listen(PORT, function (err) { if (err) console.log(err); console.log( "Server listening on PORT" , PORT); }); |
Steps to run the program:
Step 2: Run the index.js file using the below command:
node index.js
Output: Now make a POST request to http://localhost:3000/ with header set to ‘content-type: application/json’ and body {“name”:”w3wiki”}, then you will see the following output on your console:
Server listening on PORT 3000
TypeError: Cannot read property 'name' of undefined
Express JS express.json() Function
The express.json() function is a built-in middleware function in Express. It parses incoming requests with JSON payloads and is based on body-parser.
Syntax:
express.json( [options] )
Parameters: The options parameter has various properties like inflate, limit, type, etc.
Return Value: It returns an Object.