function calcularTotal(n_elem) {

    var elems = [];
    var total = 0;
    var iva = 0;
    var total_pedido = 0;

    for (var i=0; i<n_elem; i++) {
        elems.push();
        var c = Number(document.getElementById("c" + String(i)).value);
        var p = Number(document.getElementById("p" + String(i)).innerHTML);

        var t = c * p;
        total += t;
        document.getElementById("t" + String(i)).innerHTML = formatearCampo(t);
    }

    iva = total*0.18;
    total_pedido = total+iva;

    var elem_total = document.getElementById("total");
    var elem_iva = document.getElementById("iva");
    var elem_total_pedido = document.getElementById("total_pedido");
    elem_total.innerHTML = formatearCampo(total);
    elem_iva.innerHTML = formatearCampo(iva);
    elem_total_pedido.innerHTML = formatearCampo(total_pedido);
}

function formatearCampo(sVal) {
    var nDec = 2;
    var n = parseFloat(sVal);
    var s = "0.00";
    if (!isNaN(n)){
     n = Math.round(n * Math.pow(10, nDec)) / Math.pow(10, nDec);
     s = String(n);
     s += (s.indexOf(".") == -1? ".": "") + String(Math.pow(10, nDec)).substr(1);
     s = s.substr(0, s.indexOf(".") + nDec + 1);
    }
    return s;
}

function addPedidoEvents(n_elem) {
    for (var i=0; i<n_elem; i++) {
        var elem = document.getElementById("c" + String(i));
        elem.onchange = elem.onkeyup = function () {
            calcularTotal(n_elem);
        }
    }
    calcularTotal(n_elem);
}