Introduction to Web APIs

Web applications play an important role in the exchange of information between customers and businesses. Most businesses these days use web applications as it is a cost-effective way of exchanging information. It also serves as a means to help in the growth of the business in the global market.

Web applications are also popular because they are easily accessible using a web browser and can be accessed from almost any device irrespective of the location. This is because web browsers come pre-installed on all the devices such as mobile, desktop computers, tablets, etc.

To enhance user experience, developers build services for web applications using Web APIs. In this post let us understand in detail what are Web APIs along with their uses and features.

Table of Content:

1. What are APIs?
2. What are Web APIs?
3. Features of Web API
4. HTTP Methods
5. Connecting to a Web API
6. Uses of a Web API
7. Wrapping Up

What are APIs?

Before getting into Web APIs, let us understand first what is APIs. APIs stand for Application Programming Interfaces. APIs can be considered as intermediaries or messengers that facilitate communication between two applications or between a user and an application. The API receives a request and gives a response in return. For instance, when a user browses web applications like Facebook, YouTube, etc the API receives a request from the user and performs the required functionality which is the response.

APIs enable developers to build complex functionalities effortlessly since APIs allow functionalities to be reused. This helps developers as they do not have to write complex functionalities from scratch. APIs define functionalities that are independent of their implementations.

What are Web APIs?

Web API is an open-source framework that allows developers to build Web Services. This framework implements HTTP protocols and hence they are also known as HTTP APIs. Web APIs allow interaction or communication between users and a device or between two applications. Web Services built using APIs help to improve the ease of use. Generally, users interact with APIs through a web application. Developers can build Web APIs using different programming languages such as Java, .NET, etc. and can connect to Web APIs using languages such as JavaScript.

Features of Web API

• It supports basic CRUD (Create Read Update and Delete) operations.
• It also supports multiple text formats like XML and JSON.
• Responses have HTTP status code which helps users to understand whether the API request was successful or not and whether the response was received or not.
• One popular Web API is the ASP.NET Web API.
• It is open-source.

HTTP Methods

To understand Web APIs and their use, we need to understand HTTP Methods. HTTP methods are different functionalities of the HTTP protocol which helps to interact with the web. The different HTTP methods are as follows:

• HTTP GET - GET Requests are generally used to request a resource from a web application and not to modify it in any way. GET requests are considered to be safe methods since they do not allow any modification of a Web Resource.
• HTTP POST - The POST method is used to create new resources. For instance, POST methods can be used to insert new data into the database.
• HTTP PUT - The PUT method is generally used to modify existing resources entirely on the web application. PUT requests are generally made on a single resource whereas POST requests are made on a collection of resources.
• HTTP DELETE - As the name suggests, DELETE requests are used to delete an existing resource from a web application.
• HTTP PATCH - The PATCH method is used to partially update an existing resource. For example, if a user login has been created and you want to change the password, the patch method is used since the whole row has not been modified but only the password section has been modified.

Connecting to a Web API

In this part, we will learn how to connect to a Web API to access and modify data using JavaScript. For instance, let's suppose our objective is to connect to a bookstore web application and retrieve book details from its API.

To connect to the Web API we require the API endpoint. Let’s say the URL of the API endpoint is https://samplebookstore.com/books. Clicking on this link displays an array of objects in JSON format.

Now we will write our script.js file to connect to the API endpoint and retrieve data from it.

This is how our script.js file looks. The file helps to establish a connection to the API endpoint and retrieve the title of books.

Initially, we create a request variable and assign an XMLHttpRequest object to it. After that we open a new connection to the API endpoint with the open() method where we specify the details of the URL API endpoint and the type of request as GET. Once the request completes, then we access the data using the onload() function.

We retrieve the data by parsing the response received using the JSON.parse() method and we use the data variable to store all the JSON data as an array of JSON objects.

Now using our if statement, we check whether our request was successful or not. If our request was successful we use a ‘for loop’ to loop through the JSON objects and retrieve the book title and display it in the console.

Finally, we send our request to the web application.

Uses of a Web API

Some of the important uses of Web APIs are as follows:

• Web APIs are used to retrieve data resources from a web application and allow the addition of new resources and the modification of existing resources.
• Web APIs are used to build Web Services that are lightweight, maintainable, and easily scalable.
• It can even be used to create RESTful web services. REST stands for Representational State Transfer.
• Web APIs help in easy communication of devices and web applications.
• Web APIs are best to use when developers want to create resource-oriented services.
• It helps in the fast and efficient development of web services.

Wrapping Up

Through this post, you would have got a basic understanding of APIs and Web APIs. We have also seen how to connect to an API endpoint to retrieve data resources from a web application This will help you to connect to your desired APIs and retrieve data in the future. The best part is it is open-source which means you do not have to spend anything to explore it.