Ajax VS XMLHttpRequest - which one to chose?


Ajax and XMLHttpRequest are both technologies used to create asynchronous web applications, but they are not the same thing. In this blog post, we will explore the differences between the two and provide examples of how they can be used.


What is Ajax?

Ajax stands for Asynchronous JavaScript and XML. It is a technique used to create fast and dynamic web pages. It allows for the exchange of data between a web page and a server without the need to refresh the entire page. This makes for a smoother and more responsive user experience.


Ajax is a combination of technologies that work together to create dynamic web pages. The main technologies used in Ajax are:


  • • JavaScript, which is used to make the request to the server and handle the response.

  • • XMLHttpRequest (XHR), which is an API that allows for the exchange of data between a web page and a server.

  • • The Document Object Model (DOM), which is used to update the web page based on the response from the server.


Ajax is often used to create web pages that feel more like desktop applications. This is because it allows for real-time updates and interactions without the need to refresh the entire page. For example, an email application that uses Ajax can automatically update the inbox without the need for the user to manually refresh the page.


Ajax is also used to create single-page applications (SPAs). These are web pages that load a single HTML page and dynamically update the content as the user interacts with the application. This eliminates the need to load multiple pages and improves the overall user experience.


Ajax can also be used to create web services and other web applications. For example, a weather application that uses Ajax can retrieve the current weather conditions from a web service and display them on the web page without the need to refresh the entire page.


One of the main benefits of Ajax is that it allows for the exchange of data between a web page and a server without the need to refresh the entire page. This improves the overall user experience and makes web pages feel more like desktop applications. It also reduces the amount of data that needs to be transferred between the web page and the server, which can improve the overall performance of the web page.


Another benefit of Ajax is that it allows for real-time updates and interactions without the need to refresh the entire page. This can improve the overall user experience and make web pages feel more like desktop applications.


Ajax is also flexible and can be used with any programming language, such as JavaScript, PHP, or Ruby. It also allows for the use of other data formats besides XML, such as JSON, HTML, and plain text. This makes it easy to create web services and other web applications that can be consumed by different types of clients.


There are also libraries and frameworks available that make it easier to use Ajax, such as jQuery and AngularJS. These libraries provide a simplified syntax for making requests and handling responses, and they also provide other features such as animation and event handling.


Despite the benefits of Ajax, there are also some drawbacks. One of the main drawbacks is that it requires JavaScript to be enabled on the client side. This can be a problem for users who have JavaScript disabled or for users who are using an older browser that does not support JavaScript.


Another drawback of Ajax is that it can be difficult to implement. It requires a good understanding of JavaScript, XHR, and the DOM, and it can be difficult to debug and test.


Overall, Ajax is a powerful technique for creating fast and dynamic web pages. It allows for the exchange of data between a web page and a server without the need to refresh the entire page, improves the overall user experience and makes web pages feel more like desktop applications. It also allows for real-time updates and interactions, and it can be used with any programming language and data format. However, it requires JavaScript to be enabled and can be difficult to implement, making it a technique that should be used with caution and after careful consideration of the potential drawbacks.


One thing to keep in mind is that Ajax is not a standard and not all browsers support it in the same way, which can make cross-browser compatibility an issue. Additionally, search engines and other crawlers may have trouble indexing content that is loaded dynamically via Ajax, which can have an impact on SEO. Therefore, it's important to consider these factors when deciding to use Ajax in a project, and to test for compatibility and SEO implications.


In conclusion, Ajax is a powerful technique that can significantly enhance user experience and improve the performance of web pages and web applications. It allows for the exchange of data between a web page and a server without the need to refresh the entire page and enables real-time updates and interactions. However, it's important to carefully consider the potential drawbacks and to test for compatibility and SEO implications before using it. It's also worth noting that there are other technologies like Fetch API, WebSockets and WebRTC that can be used for similar purposes and may be more suitable for certain projects.


What is XMLHttpRequest?

XMLHttpRequest (XHR) is an API (Application Programming Interface) that allows for the exchange of data between a web page and a server. It is the underlying technology that makes Ajax possible. XHR is supported by all modern web browsers and is often used to create dynamic web pages, web services, and other web applications.


XHR is a JavaScript object that can be used to make HTTP requests to a server and receive the response. The API provides methods for opening a connection to a server, sending a request, receiving a response, and handling the response.


The XHR API supports both synchronous and asynchronous requests. Synchronous requests block the execution of JavaScript until a response is received, while asynchronous requests do not. Asynchronous requests are typically used in web applications as they allow the user to continue interacting with the page while the request is being processed.


XHR can be used to make a variety of different types of requests, such as GET, POST, PUT, and DELETE. It can also be used to send and receive different types of data, such as XML, JSON, and plain text.


One of the main benefits of XHR is that it allows for the exchange of data between a web page and a server without the need to refresh the entire page. This improves the overall user experience and makes web pages feel more like desktop applications.


Another benefit of XHR is that it can be used to create web services and other web applications. For example, a weather application that uses XHR can retrieve the current weather conditions from a web service and display them on the web page without the need to refresh the entire page.


XHR also allows for real-time updates and interactions without the need to refresh the entire page. This can improve the overall user experience and make web pages feel more like desktop applications.


XHR has been supported by all major web browsers for many years, which makes it a widely available and well-established technology. This means that web developers can rely on the fact that the majority of users will be able to use the web applications that they create using XHR.


However, there are also some drawbacks to using XHR. One of the main drawbacks is that it requires a good understanding of JavaScript and web applications to use effectively. It can also be difficult to debug and test, as it requires the developer to handle the different states of the request and response.


Another drawback of XHR is that it is limited to XML as the data format. This means that if you want to work with other data formats, such as JSON or HTML, you will have to write additional code to handle the conversion.


In conclusion, XHR is a powerful API that allows for the exchange of data between a web page and a server without the need to refresh the entire page. It is supported by all major web browsers, and it can be used to create web services and other web applications. However, it requires a good understanding of JavaScript and web applications, and it can be difficult to debug and test. Additionally, it's limited to XML as the data format, making it less flexible than other technologies such as Fetch API, WebSockets and WebRTC.


Differences between Ajax and XMLHttpRequest

While Ajax and XHR are often used interchangeably, they are not the same thing. Ajax is a technique that uses XHR to create dynamic web pages, while XHR is a technology that allows for the exchange of data between a web page and a server.


Ajax is a higher-level abstraction that makes it easier to use XHR. It provides a simplified syntax for making requests and handling responses, and it can be used with any programming language, such as JavaScript, PHP, or Ruby. On the other hand, XHR is a lower-level API that requires more knowledge of how web applications work and it's limited to JavaScript.


Ajax also allows for the use of other data formats besides XML, such as JSON, HTML, and plain text. XHR, on the other hand, is limited to XML as the data format.


Code Examples

Here is an example of how to make an Ajax request using the jQuery library:


$.ajax({
    url: 'example.php',
    type: 'POST',
    data: { name: 'John', age: 30 },
    success: function(response) {
        console.log(response);
    },
    error: function(e) {
    console.log(e);
 }
});

In this example, we are sending a POST request to the server-side script "example.php" with data in the form of an object. The success callback function will be executed when the server responds with a success status code, and the response data will be passed as an argument.

Here is an example of how to make an XMLHttpRequest:


var xhr = new XMLHttpRequest();
xhr.open('GET', 'example.php', true);
xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
        console.log(xhr.responseText);
    }
};
xhr.send();

XMLHttpRequest (XHR) provides a status property that contains the status code of the response from the server. The status code is a three-digit number that indicates the outcome of the request.


Here are some of the most common status codes:


  • • 200 OK: The request was successful and the server returned the requested data.

  • • 201 Created: The request was successful and the server created a new resource as a result.

  • • 204 No Content: The request was successful, but the server did not return any data.

  • • 400 Bad Request: The request was malformed or invalid.

  • • 401 Unauthorized: The request requires authentication, and the user is not authenticated.

  • • 403 Forbidden: The request is valid, but the server is refusing to fulfill it.

  • • 404 Not Found: The requested resource could not be found on the server.

  • • 500 Internal Server Error: An error occurred on the server, and the request could not be completed.


It's worth noting that these are just a few examples of the many status codes that exist, and it's important to handle different status codes appropriately in your code.


Additionally, status codes in the 100 and 300 range are also used for informational and redirectional purposes. For example, status code 100 (Continue) is used to indicate that the initial part of a request has been received and that the client should continue sending the request body, and status code 300 (Multiple Choices) is used to indicate that the requested resource has multiple representations, such as different languages or data formats.


In summary, the XHR status property is a useful tool for determining the outcome of a request and handling the response appropriately. It's important to understand the meaning and implications of the different status codes and to handle them correctly in your code.


In this example, we are sending a GET request to the server-side script "example.php". The onreadystatechange event is used to handle the response from the server. The readyState property tells us the state of the request and the status property tells us the status code of the response. Once the readyState is 4 and the status is 200, we know that the response is complete and successful, and we can access the response data using the responseText property.


Conclusion

Ajax and XMLHttpRequest are both powerful technologies for creating dynamic web applications. Ajax is a higher-level abstraction that makes it easier to use XHR, while XHR is a lower-level API that requires more knowledge of how web applications work. While both can be used to create fast and responsive web pages, they have their own unique features and limitations.

Ajax allows for the use of different data formats, such as JSON, HTML, and plain text, while XHR is limited to XML. Ajax also provides a simplified syntax for making requests and handling responses, while XHR requires more code to accomplish the same task.


In conclusion, whether you choose to use Ajax or XHR will depend on the specific requirements of your project. Both technologies have their own strengths and weaknesses, and it's important to choose the right tool for the job. If you're looking for a higher-level abstraction that is easy to use and supports different data formats, Ajax is a great choice. But if you're looking for a lower-level API that provides more control and requires more knowledge of web applications, XHR is the way to go.


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