Calling Ajax in Javascript: A Step-by-Step Guide

Have you ever wondered how some websites are able to update information without having to refresh the page? Or how some websites are able to load new content without you having to navigate to a new page? The answer to both of those questions is Ajax. Ajax, or Asynchronous JavaScript and XML, is a technique used in web development to make asynchronous requests to the server without having to reload the page. This technique has become increasingly popular in the last few years due to its ability to create a more seamless user experience. In this step-by-step guide, we will walk you through the process of calling Ajax in Javascript.

Understanding Ajax

Before we dive into the specifics of calling Ajax in Javascript, it is important to understand what Ajax is and how it works. Ajax is a technique that allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes. This means that a user can interact with a web page without having to wait for a complete page reload.

Ajax works by using the XMLHttpRequest object, which is built into most modern web browsers. This object allows Javascript to send requests to the server and receive responses without having to reload the page. When an Ajax request is made, the browser sends a request to the server in the background. The server then processes the request and sends a response back to the browser. Once the response is received, Javascript can manipulate the DOM to update the page with the new data.

Step 1: Creating the XMLHttpRequest Object

The first step in calling Ajax in Javascript is creating the XMLHttpRequest object. This object is what allows Javascript to send requests to the server and receive responses.

var xhttp = new XMLHttpRequest();

This creates a new XMLHttpRequest object and assigns it to the variable xhttp.

Step 2: Sending the Request

Once the XMLHttpRequest object has been created, the next step is to send the request to the server. This is done using the open() and send() methods.

xhttp.open("GET", "example.php", true);
xhttp.send();

The open() method takes three arguments: the HTTP method (GET or POST), the URL to send the request to, and a boolean value indicating whether the request should be asynchronous (true) or synchronous (false). In most cases, you will want to make the request asynchronous so that the user can continue to interact with the page while the request is being processed.

The send() method sends the request to the server. If the request is a GET request, the data is sent as part of the URL. If the request is a POST request, the data is sent in the body of the request.

Step 3: Handling the Response

Once the request has been sent to the server, the next step is to handle the response. This is done using the onreadystatechange event.

xhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    // Do something with the response
  }
};

The onreadystatechange event is fired whenever the state of the XMLHttpRequest object changes. In this case, we are checking to see if the readyState is equal to 4 and the status is equal to 200. This indicates that the response has been received and is ready to be processed.

Step 4: Processing the Response

The final step in calling Ajax in Javascript is processing the response. This is done using the responseText or responseXML property of the XMLHttpRequest object.

xhttp.onreadystatechange = function() {
  if (this.readyState == 4 && this.status == 200) {
    document.getElementById("demo").innerHTML = this.responseText;
  }
};

In this example, we are using the responseText property to update the innerHTML of an element with the ID "demo". This will update the page with the response from the server.

Final Thoughts

Ajax is a powerful technique that can be used to create a more seamless user experience on the web. By using Ajax, web developers can update information on a web page without having to refresh the page or navigate to a new page. In this step-by-step guide, we have walked you through the process of calling Ajax in Javascript. By following these steps, you can start using Ajax in your own web development projects to create a more dynamic and interactive user experience.

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