Send Uploaded file to API with AJAX Request [duplicate]

I am testing some API functions through localhost using an HTML website with ajax to make this api calls, everything works great till i bumped to this api call:

localhost/uploadFile?file=?????&userID=123421

I have searched everywhere about a way to upload a file and send it with API but could not find anything helpful, what I know about this API call(uploadFile) is that it can only be a POST request.

So this is what I do:

HTML Code:

<form method="post" id="form">
<input type="file" name="file" id="file">
<button type="submit" onclick="check(this.form)" id="submitbtn" >Send</button>
</form>

Ajax Script:

function check(form){

     $.ajax({
        url: "http://localhost/uploadFile&file="+document.getElementById("file").value+"&userID=123421",
        type: "POST",
        dataType: "json",
        success: function (result) {
            switch (result) {
                case true:
                    alert(result);
                    break;
                default:
                    alert(result);
            }
        },
        error: function (xhr, ajaxOptions, thrownError) {
        alert(xhr.status);
        alert(thrownError);
        }
    });
}

I found this tutorial to use ajax to upload a file but it only saves it to the server how can I send it with the api? The mystery is in the parameter file what can I save there?? I printed the value of document.getElementById("file").value and it's just somthing like C:/fakepath/fileName.txt, If you have any idea how this works would be very helpful I am new to ajax and I am open to other web programming languages, except php for some api reasons...