**Node.js** is a compatible runtime scenario for compiling JavaScript code outside of a browser. It was created on Chrome's Javascript Engine. The Express.js functions between request and response cycles. It's a Middleware framework for managing the routing of different web pages. A Middleware can request:
* An object 
* Response object 
* The next function that calls the next Middleware



app.get(path, (req, res, next) => {}, (req, res) => {})

`(req, res, next) => {}`: The Middleware function. It defines actions to be done before the webpage can be viewed and other functions can be called.

import React from 'react';
require('./style.css');

import ReactDOM from 'react-dom';
import App from './app.js';

ReactDOM.render(
  <App />, 
  document.getElementById('root')
);


import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


React

Dart

GoJS React

Typescript React

Vue.js

mern_image.tar.gz

What is Node.js Middleware?

Node.js runs JavaScript outside browsers. Middleware manages routing and actions before web pages load using request, response, and next function constructs.

What is Node.js Middleware?

Overview

Middleware syntax

Creating middleware

Example

Explanation