Avoiding Duplicate AJAX Requests

Introduction

When working with AJAX requests, duplicate API calls can lead to performance issues, unnecessary server load, increased bandwidth usage, and inconsistent data handling.

Common Scenarios Where Duplicate Requests Occur

🔹 Fast clicking on buttons that trigger AJAX requests
🔹 Rapid typing in a search box with AJAX-based suggestions
🔹 Scrolling that triggers AJAX calls multiple times
🔹 Unintentional page reloads causing repeated API calls
🔹 Multiple event bindings causing redundant requests

To prevent duplicate AJAX requests, we can apply several optimization techniques like:

✅ Request tracking mechanisms
✅ Debouncing and throttling
✅ Caching API responses
✅ Using flags to prevent multiple requests
✅ Abort previous AJAX requests

1️⃣ Understanding the Problem of Duplicate AJAX Requests
2️⃣ Using Flags to Prevent Duplicate Requests
3️⃣ Using Debounce to Avoid Frequent Calls
4️⃣ Using Throttle to Limit Request Rate
5️⃣ Aborting Previous AJAX Requests
6️⃣ Caching API Responses to Prevent Redundant Calls
7️⃣ Preventing Duplicate Submissions in Forms
8️⃣ Avoiding Multiple Event Bindings in jQuery
9️⃣ Implementing Request Deduplication with Promises
🔟 Best Practices for Managing AJAX Requests
📌 Conclusion

1. Understanding the Problem of Duplicate AJAX Requests

When AJAX requests are triggered multiple times unintentionally, they can:

⚠ Overload the server with redundant requests
⚠ Slow down performance due to excessive network calls
⚠ Show outdated data if multiple responses overwrite each other
⚠ Cause inconsistent UI behavior

2. Using Flags to Prevent Duplicate Requests

A simple and effective way to prevent duplicate AJAX calls is by using flags.

🔹 How It Works:

Set a flag (isRequestInProgress = true) when an AJAX request starts.
Check the flag before making a new request.
Reset the flag (isRequestInProgress = false) once the request completes.

🔹 Example: Using a Flag to Prevent Multiple Requests

let isRequestInProgress = false;

function fetchData() {
    if (isRequestInProgress) return;  // Prevent duplicate calls

    isRequestInProgress = true;  // Set flag

    $.ajax({
        url: "https://api.example.com/data",
        type: "GET",
        success: function(response) {
            console.log("Data received:", response);
        },
        complete: function() {
            isRequestInProgress = false;  // Reset flag
        }
    });
}

// Attach event listener
document.getElementById("fetchButton").addEventListener("click", fetchData);

✅ Benefits:
✔ Prevents unnecessary AJAX calls
✔ Ensures only one active request at a time

3. Using Debounce to Avoid Frequent Calls

📌 Debouncing delays the AJAX request until the user stops interacting.

🔹 Ideal For:
✔ Search boxes
✔ Live filters
✔ Input fields

🔹 Example: Debouncing API Calls in a Search Box

function debounce(func, delay) {
    let timer;
    return function (...args) {
        clearTimeout(timer);
        timer = setTimeout(() => func.apply(this, args), delay);
    };
}

document.getElementById("searchBox").addEventListener("input", debounce(function (e) {
    fetch(`https://api.example.com/search?q=${e.target.value}`)
        .then(response => response.json())
        .then(data => console.log("Search results:", data));
}, 500));  // Executes after 500ms of inactivity

✅ Benefits:
✔ Reduces unnecessary API calls
✔ Improves performance and server efficiency

4. Using Throttle to Limit Request Rate

📌 Throttling ensures that an AJAX request is triggered only once per time interval.

🔹 Ideal For:
✔ Scroll events
✔ Resizing windows
✔ Rapid clicks

🔹 Example: Throttling AJAX Calls

function throttle(func, interval) {
    let lastCall = 0;
    return function (...args) {
        const now = Date.now();
        if (now - lastCall >= interval) {
            func.apply(this, args);
            lastCall = now;
        }
    };
}

window.addEventListener("scroll", throttle(function () {
    fetch("https://api.example.com/scrollData")
        .then(response => response.json())
        .then(data => console.log("Loaded data:", data));
}, 1000)); // Limits to one call per second

✅ Benefits:
✔ Reduces request frequency
✔ Optimizes scrolling performance

5. Aborting Previous AJAX Requests

📌 If a new AJAX request is triggered, the previous one should be canceled.

🔹 Example: Canceling an Ongoing AJAX Request

let ajaxRequest;

function fetchData(query) {
    if (ajaxRequest) {
        ajaxRequest.abort(); // Cancel previous request
    }

    ajaxRequest = $.ajax({
        url: `https://api.example.com/search?q=${query}`,
        type: "GET",
        success: function(response) {
            console.log("Latest data:", response);
        }
    });
}

document.getElementById("searchBox").addEventListener("input", function (e) {
    fetchData(e.target.value);
});

✅ Benefits:
✔ Ensures only the latest request is processed
✔ Reduces redundant network traffic

6. Caching API Responses to Prevent Redundant Calls

📌 If the same request is made multiple times, cache the response.

🔹 Example: Simple AJAX Caching Mechanism

let cache = {};

function fetchCachedData(url) {
    if (cache[url]) {
        console.log("Using cached data:", cache[url]);
        return Promise.resolve(cache[url]);
    }

    return fetch(url)
        .then(response => response.json())
        .then(data => {
            cache[url] = data;
            console.log("Fetched new data:", data);
            return data;
        });
}

// Example usage
fetchCachedData("https://api.example.com/data");
fetchCachedData("https://api.example.com/data"); // This will use the cached result

✅ Benefits:
✔ Reduces repeated API requests
✔ Improves response time

7. Preventing Duplicate Submissions in Forms

📌 Prevent users from submitting a form multiple times.

🔹 Example: Disabling the Submit Button Until Completion

document.getElementById("submitBtn").addEventListener("click", function () {
    let button = this;
    button.disabled = true;

    $.ajax({
        url: "https://api.example.com/submit",
        type: "POST",
        data: { name: "John" },
        success: function(response) {
            console.log("Form submitted successfully!");
        },
        complete: function() {
            button.disabled = false; // Re-enable button
        }
    });
});

✅ Benefits:
✔ Prevents duplicate form submissions

8. Avoiding Multiple Event Bindings in jQuery

📌 Ensure an event listener is bound only once.

🔹 Example: Using off() Before Binding

$("#fetchButton").off("click").on("click", function () {
    fetchData();
});

✅ Benefits:
✔ Prevents duplicate event bindings

9. Implementing Request Deduplication with Promises

📌 Ensure that only one request per unique query is processed at a time.

🔹 Example: Deduplicating API Requests

let ongoingRequests = {};

function fetchUniqueData(url) {
    if (ongoingRequests[url]) return ongoingRequests[url];

    ongoingRequests[url] = fetch(url)
        .then(response => response.json())
        .finally(() => delete ongoingRequests[url]); // Remove request from tracking

    return ongoingRequests[url];
}

✅ Benefits:
✔ Prevents duplicate API calls for the same data

Avoiding duplicate AJAX requests is crucial for performance optimization. Techniques such as flags, debounce, throttle, aborting requests, caching, and event binding control help eliminate redundant requests.

By implementing these best practices, you can improve API efficiency, enhance user experience, and optimize application performance.

Avoiding duplicate AJAX requests