creating generic ajax method

hi all,

I am trying to create a generic AJAX method for calling on a site

function runAjax(webmethod, fieldname, fieldtext) {
    
    return $.ajax({
        type: "POST",
        url: webmethod,
        data: JSON.stringify({ username: fieldtext }),
        contentType: "application/json; charset=utf-8",
        dataType: "json"
    });
}

Select allOpen in new window

the above code works fine, however when I substitute username to fieldname (i.e. to the passed variable, the method doesnt fire?

Is there anyway I can inject the fieldname text into this method?

thanks.