How does Node. js respond to Ajax POST requests and save them as JSON files?

How does Node. js respond to Ajax POST requests and save them as JSON files?

Purpose

How can a front-end application developed using D3.js show the last interactive content of a graph after the user interacts with the graph to change its content?

This article provides a minimal solution through the back-end Node. js program as a reference.

Development Environment

• Backend: Node. js
• Node. js modules: Express, body-parser, fs
• Front-end: JQuery
  

Backend

1. Install nodejs. Use the displayed version number to check whether node. JS is installed.

node --version

2. Create a project directory (folder) and install the module.

npm install expressnpm install body-parser

Express is a Node. js Web application framework: http://expressjs.com/

BodyParser is used to parse the http Request body: https://github.com/expressjs/body-parser

3. Create a createServer. js

Var express = require ('express '); var bodyParser = require ('body-parser'); var fs = require ('fs'); var app = express (); // bodyParser. urlencoded parses the data app submitted by form. use (bodyParser. urlencoded ({extended: false}); // bodyParser. json parses the app in json data format. use (bodyParser. json (); app. post ('/saveJSON', function (req, res) {// convert an object to a string var str_json = JSON. stringify (req. body); fs. writeFile ('graph. json ', str_json, 'utf8', function () {// The console of the callback function after saving. log ("saved") ;};}); app. listen (0, 3000 );

4. Run createServer. js.

Node createServer.js

It monitors requests sent from http: // 127.0.0.1: 3000.

If the request comes from: http: // 127.0.0.1: 3000/saveJSON, it will save a graph. json file in the Server Directory, which contains post data sent by the client.

Front end

// Create an object var person = {name: "lucy", age: 25} // send a POST request with JQuery, whose content is person $. post ("http: // 127.0.0.1: 3000/saveJSON", person, function (data, status) {alert ("Data:" + data + "\ nStatus: "+ status );});

After loading in the browser, the backend console displays "Save complete", which is the callback function we wrote in writeFile. A graph. json file is added to the server directory to verify that the result is correct.

Summary

The above is all about this article. I hope this article will help you in your study or work. If you have any questions, please leave a message. Thank you for your support.