How can i get the value of multiple anchors in javascript which are generated from php and send the value to another Php page using AJAX

Here is how my anchors are displayed on the web. I need to get the value of the anchor and send it to another PHP file, so i would use the value of the anchor in my SQL query to give the condition to display all the productId associated with the value of the anchor

                       <?php
                        include"validations/connection.php";
                        $sql = "SELECT * from category ORDER BY CHAR_LENGTH(categoryName)";
                        $result = $conn->query($sql);

                        if ($result->num_rows > 0) {

                            echo'   
                                <div class="col-sm-12">
                                    <ul class="nav flex-column">
                            ';
                            while($row = $result->fetch_assoc()){
                                $id = $row['categoryId'];
                                $sqltwo = "SELECT COUNT(productId) AS num FROM products WHERE categoryId = '$id'";
                                $resultwo = $conn->query($sqltwo);
                                
                                while($rowtwo = $resultwo->fetch_assoc()){
                                    echo'
                                        <li class="nav-item">
                                            <button value="'.$row['categoryId'].'" class="link-show">'.$row['categoryName'].'</button> <span class="badge badge-danger ml-1">'.$rowtwo['num'].'</span>
                                        </li>
                                    ';
                                }
                            }
                            echo'
                                </ul><hr>
                            </div>
                            ';
                        }
                    ?>

And here is my JavaScript

<script>
    var id = document.querySelectorAll('.link-show').value;
    document.querySelectorAll('.link-show').forEach(item => {
        item.addEventListener('click', event => {
            var xhr = new XMLHttpRequest();
            xhr.open('GET','validations/retrievebycategory.php?id='+id, true);

            xhr.onload = function(){
                console.log(this.responseText);
            }
            xhr.send();
        })
    })

</script>

Answer

    // Remove this, it's querying all links
    // var id = document.querySelectorAll('.link-show').value;
    document.querySelectorAll('.link-show').forEach(item => {
        item.addEventListener('click', event => {
            
            // In the event handler, "this" is set to event.currentTarget (the button, in this case).
            // Equivalent formulations:
            // let id = event.currentTarget.value; // (from event, standard behavior, equivalent to "this")
            // let id = event.target.value // (from event's initial target, equivalent in most cases, except if the "click" is generated by a nested element; generally unsafe to use unless the intent is clear)
            // let id = item.value; // (from closure)
            let id = this.value;
            
            var xhr = new XMLHttpRequest();
            xhr.open('GET','validations/retrievebycategory.php?id='+id, true);

            xhr.onload = function(){
                console.log(this.responseText);
            }
            xhr.send();
        })
    })

See modifications and explanations in the code