Making a simple HTTP server in Node.js has become the de facto 'hello world' for the platform. On the one hand, Node.js provides extremely easy-to-use HTTP APIs; on the other hand, a simple web server also serves as an excellent demonstration of the asynchronous strengths of Node.
Express.js is a wrapper of Node.js
Express is a web application framework for Node. js that allows you to spin up robust APIs and web servers in a much easier and cleaner way. It is a lightweight package that does not obscure the core Node.
In computer science, a wrapper is any entity that encapsulates (wraps around) another item. Wrappers are used for two primary purposes: to convert data to a compatible format or to hide the complexity of the underlying entity using abstraction. Examples include object wrappers, function wrappers, and driver wrappers.
Difference Between API And Web Service
1. All Web services are APIs but all APIs are not Web services.
2. Web services might not perform all the operations that an API would perform.
3. A Web service uses only three styles of use: SOAP, REST and XML-RPC for communication whereas API may use any style for communication.
4. A Web service always needs a network for its operation whereas an API doesn’t need a network for its operation.
5. An API facilitates interfacing directly with an application whereas a Web service interacts with two machines over a network.
6.web service is like advanced Urls and API is Programmed Interface.
7.API contains classes and Interfaces just like a program.
8.A web service is a form of API (Application Programming Interface).
9.An API is used by a computer programmer to establish a link between software applications. This interface can take several forms, a web service is just one of these.
10.There are several types of web service. SOAP (Simple Object Access Protocol) is one of the most common. The API takes the form of a service description (WSDL) which is used to automatically generate the program code which makes the connection.
REST APIs are a type of Web Service APIs. A REST API is a standardized architecture style for creating a Web Service API. One of the requirements to be a REST API is the utilization of HTTP methods to make a request over a network in JSON for data format.
Web Apps
A Web Application can consist of multiple Web Services. To differentiate between two, ask what interacts with it.
Web Application: End Users via a User Interface.
Web Service: Web App / Web Service Interaction via HTTP/S requests.
For example, an E-Commerce site is in its entirety a Web Application. It has users interact with it, to purchase items. It then speaks to its appropriate Web Services to achieve what the user wants:
Order Service to place orders.
Accounts Service to register a new Customer or update their details.
Product Service to check if a particular item is in stock or to send results based on search criteria.
Web Application
A web application is a software application that a user runs in the web browser. It have the following features.
It has a User Interface
Runs in Client - Server environment
Client runs it with the help of a web browser
Server process the data based on client request and provide response
Web Service
A web service is an Application Program Interface (API) that runs on the server, which provide data to the client over http through a standardized messaging system. (XML, JSON, etc...). Web services are further classified into SOAP and REST. In the present day scenario most services prefer REST over SOAP.
Example
I'll explain a simple REST call using a GET request to the github api. You can access the details of a github user with the following request
https://api.github.com/users/<user−name>https://api.github.com/users/<user−name>
See My details in JSON format from GitHub. Click Here And such data can be integrated into a web application, mobile app, etc.
Some other use cases of Web Services are
Conclusion
Both Web Application and Web Service are a kind of same thing, but web application is for the users and Web Service is for Program <==> Program communication.