Edit in JSFiddle

var result = document.getElementById('result');

function People() {
    //properties
    this.impublic = "John Doe";
    var imprivate = "private property";
    // methods
    function imPrivate() {
        return imprivate;
    }
    this.imPrivileged = function () {
        // can call priv. methods	
        return imPrivate();
    };
}
// public methods
People.prototype.imPublic = function () {
    return this.impublic;
};
// static property
People.onlyForPeopleObject = "im accessible only from People object";
// prototype property
// visszamenőleg a többi People objektum is megkapja
People.prototype.forPrototype = "im accessible for all childs";

var person = new People();

result.innerHTML += '1: ' + person.impublic + '<br />';
result.innerHTML += '2: ' + person.imprivate + '<br />';
//hiba
try {
    result.innerHTML += '3: ' + person.imPrivate() + '<br />';
} catch(ex){
    result.innerHTML += 'Exception accessing private member.<br />';
}
result.innerHTML += '4: ' + person.imPrivileged() + '<br />';
result.innerHTML += '5: ' + person.imPublic() + '<br />';
result.innerHTML += '6: ' + person.onlyForPeopleObject + '<br />';
result.innerHTML += '7: ' + People.onlyForPeopleObject + '<br />';
result.innerHTML += '8: ' + person.forPrototype + '<br />';
result.innerHTML += '9: ' + People.forPrototype + '<br />';
result.innerHTML += '10: ' + People.prototype.forPrototype + '<br />';