Ich erstelle eine Kontakt-App, mit der eine Tabelle anhand der Benutzereingaben aktualisiert wird. Es scheint jedoch nicht, dass die Tabelle aktualisiert wird, sobald ich Daten eingebe. Es wird nur der obige Fehler angezeigt. Ich weiß nicht, wie ich die Methode ändern soll, ich habe viele verschiedene Funktionen usw. ausprobiert, aber kein Glück.

var nameField, addressField, emailField, postcodeField;

function twoDigit(v){
if(v.toString().length < 2){
    return "0"+v.toString();
} else {
    return v.toString();
}
}

var Contact = function(name, address, email, postcode){
this.name = name;
this.address = address;
this.email = email;
this.postcode = postcode;
this.completed = false;
};

var contacts = [];

Contact.prototype.toString = function(){
var s = this.name + '\n' + this.address + '\n' + this.email + + '/n'
  +  this.postcode.toString() + '\n';
if(this.completed){
    s += "Completed\n\n";
} else {
    s += "Not Completed\n\n";
}
return s;
};

var addContact = function(nameField, addressField, emailField, postcodeField){
a = new Contact(nameField.value, addressField.value, 
emailField.value, postcodeField.value);
contacts.push(a);
};

var clearUI = function(){
var white = "#fff";
nameField.value = "";
nameField.style.backgroundColor = white;
addressField.value = "";
addressField.style.backgroundColor = white;
emailField.value = "";
emailField.style.backgroundColor = white;
postcodeField.value = "";
postcodeField.style.backgroundColor = white;

};

var updateList = function(){
var tableDiv = document.getElementById("table"),
    table = "<table border='1'><thead><th>Name</th>
<th>Address</th><th>Email</th><th>Postcode</th><th>Completed</th></thead>";

for(var i=0, j=contacts.length; i<j; i++){
    var contacts1 = contacts[i];
     table += contacts1.tableRow();
}
table+="</table>";
tableDiv.innerHTML = table;
};

var add = function(){
addContact(nameField, addressField, emailField, postcodeField);
clearUI();
updateList();
};

var cancel = function(){
clearUI();
updateList();
};

window.onload = function(){
nameField = document.getElementById("name");
addressField = document.getElementById("address");
emailField = document.getElementById("email");
postcodeField = document.getElementById("postcode");
okButton = document.getElementById("ok");
okButton.onclick = add;
cancelButton = document.getElementById("cancel");
cancelButton.onclick = cancel;
clearUI();
}; 

var showTable = function(){
var tableDiv = document.getElementById("table"),
    table = "<table border='1'><thead><th>Name</th>
<th>Address</th><th>Email</th>  <th>Postcode</th></thead>";

for(var i=0, j=contacts.length; i<j; i++){
    var contacts1 = contacts[i];
    table += contacts1.tableRow();
}
table+="</table>";
tableDiv.innerHTML = table;
};