Abort Ajax requests using jQuery

About ‘AJAX’

AJAX stands for Asynchronous JavaScript and XML. It is a technique used for creating fast and dynamic web pages.

AJAX enables the use of a web page to retrieve small pieces of data from a server without having to refresh the entire page. This allows for more efficient use of bandwidth and a faster user experience.

An AJAX request is made using JavaScript, typically using a library such as jQuery, to send a request to a server-side script (such as PHP or Node.js). The server-side script processes the request and sends a response back to the web page, which can then update certain parts of the page without requiring a full page refresh.

AJAX requests are often used for tasks such as form submission, data validation, and dynamic updates to a web page, such as displaying new data or updating a graph or chart.

How to abort AJAX requests using jQuery

In jQuery, you can use the ‘.abort()’ method to abort an active AJAX request. You would typically assign the returned jqXHR object to a variable when making the request, and then pass that variable to the ‘.abort()’ method when you want to cancel the request.

Here’s an example:

var request = $.ajax({
  url: "example.php",
  type: "POST",
  data: { name : "John" }
});

// Later on, you can abort the request using
request.abort();

You can also abort all the current ajax requests by using ‘$.ajaxStop()’

Allow for Parts of a Web page to be updated dynamically with AJAX

To allow for parts of a web page to be updated dynamically with AJAX (Asynchronous JavaScript and XML), you can follow these general steps:

1. Set up an event listener on the page element that triggers the update, such as a button click or a form submission.
2. In the event listener, use the ‘XMLHttpRequest‘ (XHR) object or the newer fetch() API to send a request to the server for the updated data.
3. In the server-side code, handle the request and generate a response that contains the updated data in a suitable format, such as JSON or HTML.
4. In the client-side JavaScript code, use the response data to update the relevant part of the web page, such as a div element or a table row.

Here’s an example using ‘XMLHttpRequest‘:

// Step 1: Set up an event listener
document.getElementById("update-button").addEventListener("click", function() {
  // Step 2: Send a request to the server
  const xhr = new XMLHttpRequest();
  xhr.open("GET", "/update-data", true);
  xhr.onload = function() {
    if (this.status === 200) {
      // Step 4: Update the web page
      const updatedData = JSON.parse(this.responseText);
      document.getElementById("data-table").innerHTML = generateTableHtml(updatedData);
    }
  };
  xhr.send();
});

// Helper function to generate HTML for a table from data
function generateTableHtml(data) {
  let html = "<table><thead><tr><th>Name</th><th>Age</th></tr></thead><tbody>";
  data.forEach(function(item) {
    html += `<tr><td>${item.name}</td><td>${item.age}</td></tr>`;
  });
  html += "</tbody></table>";
  return html;
}

In this example, we set up an event listener on a button with id ‘update-button‘ that triggers the update. When the button is clicked, the JavaScript code sends a ‘GET‘ request to the server for updated data using an ‘XMLHttpRequest‘ object. In the server-side code, the request is handled and the response is generated in JSON format. In the client-side JavaScript code, the response data is parsed into a JavaScript object, and a helper function generates HTML for a table from the data. Finally, the HTML is inserted into a div element with id ‘data-table‘ using the ‘innerHTML‘ property.

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Provide Real-Time Notification using AJAX

To provide real-time notifications using AJAX (Asynchronous JavaScript and XML), you can use a technique called long polling, where the client sends a request to the server and waits for the server to respond with new data, and then immediately sends another request to keep the connection open. Here are the general steps for implementing real-time notifications using AJAX long polling:

1. Set up an event listener on the page element that triggers the notifications, such as a button click or a form submission.
2. In the event listener, use the ‘XMLHttpRequest‘ (XHR) object or the newer fetch() API to send a request to the server for the initial notification data.
3. In the server-side code, handle the request and generate a response that contains the initial notification data in a suitable format, such as JSON or HTML.
4. In the client-side JavaScript code, use the response data to display the initial notifications.
5. Set up a function that sends a new request to the server for updated notification data and calls itself recursively to keep the connection open.
6. In the server-side code, handle the new request and wait for new notification data to become available.
7. When new notification data becomes available, generate a response that contains the new data in a suitable format.
8. In the client-side JavaScript code, use the response data to update the notifications display.
9. Call the recursive function again to keep the connection open and wait for more updates.

Here’s an example using the’XMLHttpRequest‘:

// Step 1: Set up an event listener
document.getElementById("notifications-button").addEventListener("click", function() {
  // Step 2: Send a request to the server for initial notifications data
  const xhr = new XMLHttpRequest();
  xhr.open("GET", "/get-notifications", true);
  xhr.onload = function() {
    if (this.status === 200) {
      // Step 4: Display the initial notifications
      const initialData = JSON.parse(this.responseText);
      displayNotifications(initialData);
      // Step 5: Set up the recursive function
      const longPoll = function() {
        const xhr = new XMLHttpRequest();
        xhr.open("GET", "/get-notifications", true);
        xhr.onload = function() {
          if (this.status === 200) {
            // Step 8: Update the notifications display
            const newData = JSON.parse(this.responseText);
            updateNotifications(newData);
            // Step 9: Call the recursive function again
            longPoll();
          }
        };
        xhr.send();
      };
      longPoll();
    }
  };
  xhr.send();
});

// Helper function to display notifications
function displayNotifications(data) {
  // display the notifications data
}

// Helper function to update notifications
function updateNotifications(data) {
  // update the notifications display with new data
}

In this example, we set up an event listener on a button with id ‘notifications-button‘ that triggers the notifications. When the button is clicked, the JavaScript code sends a ‘GET‘ request to the server for initial notifications data using an ‘XMLHttpRequest‘ object. In the server-side code, the request is handled and the response is generated in JSON format. In the client-side JavaScript code, the response data is parsed into a JavaScript object, and a helper function displays the initial notifications. Then, a recursive function called ‘longPoll‘ is set up to keep the connection open and wait for new notification data. The ‘longPoll’ function sends a new request to the server for updated notification data and waits for the response. When the response is received, the function updates the notifications display with the new data and then calls itself again to keep the connection open and wait for more updates.