Multiple file uploads resulting in each disabled button becoming enabled

On a page I have multiple file uploads and each has its own Upload button.

When i call the type=”submit” button each file load goes off to its own controller and its file is loaded. This works nicely and the same code can be used for all file uploads $("form").submit(function (eventObj)

What i am struggling with is this: I don’t want the user to be able to press the Upload button if they have not selected a file, so i have disabled the button until a file is pressed, the disabling bit works fine. What i need help with is how when the file is selected do i call something that changes the disabled button to enabled (when user selects a file) and works for multiple file uploads using the same bit of code that can be used for all file uploads.
Is there a way to get the enable button to work a bit like this line: $("form").submit(function (eventObj) { which handles all file uploads?
I want to try to avoid having different bits of code for each file upload and keeping names like id=”filename” the same for every file upload. I can get it working for a single file upload but not multiple.

Hopefully my question makes sense, I am newish to Javascript.

Thank you in advance.

<h1>Upload Files</h1>

<form enctype="multipart/form-data" asp-action="UploadFile" asp-controller="Ls" method="post">
    <dl>
        <dd>
            <input type="file" name="file" id="filename">             
            
        </dd>
    </dl>
    <input class="btn btn-primary" id="uploadButton" type="submit" value="Upload" disabled/>
</form>


<form enctype="multipart/form-data" asp-action="UploadFile" asp-controller="Cv" method="post">
    <dl>
        <dd>
            <input name="file" type="file" id="filename">            
        </dd>
    </dl>
    <input class="btn btn-primary" id="uploadButton" type="submit" value="Upload" disabled/>
</form>
   //there are more of these upload forms



@section Scripts {
    <script>    
        filename.onchange = function(eventObj)  {
                //this works but only for the first file upload not the other ones.
                if($(this).val())
                {
                    $("#uploadButton").prop("disabled", false);
                }
                else
                {
                    $("#uploadButton").prop("disabled", true);
                }
        };

        $("form").submit(function (eventObj) {                        
           //some stuff
            var formData = new FormData(eventObj.currentTarget);                  
            
            $.ajax({
                url : eventObj.currentTarget.action,
                type: "POST",
                data : formData,
                processData: false,
                contentType: false,
                cache: false,
                enctype: 'multipart/form-data',   
               
                success:function(data, textStatus, jqXHR){                    
                    console.log("in success");                   
                },
                error: function(jqXHR, textStatus, errorThrown){                      
                }
            });            
            return false;            
        }); 
    </script>
}