function emptyInput(naam,waarde)  {
                                  if(document.getElementById(naam).value == waarde)
                                    {
                                    document.getElementById(naam).value = "";
                                     }
                                   }

function checkCalculation()  {

    var calculate_omzet = document.getElementById("calculate_omzet").value;
    var calculate_kosten_inkoop = document.getElementById("calculate_kosten_inkoop").value;
    var calculate_kosten_overig = document.getElementById("calculate_kosten_overig").value;

    if (calculate_omzet == '') {

            document.getElementById("home_calculation_title").innerHTML = "Vult u a.u.b. een omzet in";
            document.getElementById("home_calculation_title").style.color = "#ff0000";
            document.getElementById("calculate_omzet").className = "input_calculate_fout";

    }

    else if (calculate_kosten_inkoop == '') {

            document.getElementById("home_calculation_title").innerHTML = "Er zijn geen kosten inkoop ingevuld";
            document.getElementById("home_calculation_title").style.color = "#ff0000";
            document.getElementById("calculate_kosten_inkoop").className = "input_calculate_fout";
            document.getElementById("calculate_omzet").className = "input_calculate";

    }

    else if (calculate_kosten_overig == '') {

            document.getElementById("home_calculation_title").innerHTML = "Het veld Kosten overig is nog leeg";
            document.getElementById("home_calculation_title").style.color = "#ff0000";
            document.getElementById("calculate_kosten_overig").className = "input_calculate_fout";
            document.getElementById("calculate_kosten_inkoop").className = "input_calculate";

    }

    else {

    var totale_kosten = parseFloat(calculate_kosten_inkoop)+parseFloat(calculate_kosten_overig);
    var bruto_winst = parseFloat(calculate_omzet)-parseFloat(totale_kosten);
    var besparing = 0.03*parseFloat(calculate_kosten_inkoop);
    var new_kosten_inkoop = parseFloat(calculate_kosten_inkoop)-parseFloat(besparing);
    var new_totale_kosten = parseFloat(new_kosten_inkoop)+parseFloat(calculate_kosten_overig);
    var new_bruto_winst = parseFloat(calculate_omzet)-parseFloat(new_totale_kosten);

            document.getElementById("home_calculation_title").innerHTML = "De bruto winst is berekend";
            document.getElementById("calculate_kosten_overig").className = "input_calculate";
            document.getElementById("calculate_totale_kosten").value = totale_kosten;
            document.getElementById("calculate_bruto_winst").value = bruto_winst;
            document.getElementById("calculate_new_bruto_winst").value = new_bruto_winst;
            document.getElementById("home_calculation_title").style.display = "none";
            document.getElementById("home_calculation_title_verstuurd").style.display = "block";

    }


         }