String.prototype.trim = function()
    {
        return this.replace(/^\s*|\s*$/g, "");
    };

    function is_valid_email(str)
    {
        var regex = /^[a-zäöü0-9]+([_\.\-][a-zäöü0-9]+)*@([a-zäöü0-9]*([\.\-][a-zäöü0-9]{2,})*)+\.[a-zäöü]{2,6}$/i;
        var rgx = new RegExp(regex);
        return rgx.exec(str) ? true : false;
    }

    function validate(elems)
    {
        var errors = new Array();
        var options;
        var selections;
        var checked;
        var valid;
        var err;
        
        for(var i in elems)
        {
            switch(elems[i][0])
            {
                case "text":
                    if(document.getElementById(elems[i][2]).value.trim().length < elems[i][1])
                    {
                        errors.push(elems[i][3]);
                    }
                break;
                case "email":
                    if(!is_valid_email(document.getElementById(elems[i][1]).value))
                    {
                        errors.push(elems[i][2]);
                    }
                break;
                case "multiple":
                    options = document.getElementById(elems[i][2]).childNodes;
                    selections = 0;
                    for(var j in options)
                    {
                        if(options[j].nodeName == "option" || options[j].nodeName == "OPTION")
                        {
                            if(options[j].selected)
                            {
                                selections ++;
                            }
                        }
                    }
                    if(selections < elems[i][1])
                    {
                        errors.push(elems[i][3]);
                    }
                break;
                case "radio":
                    checked = false;
                    for(var j in elems[i][1])
                    {
                        if(document.getElementById(elems[i][1][j]).checked == true)
                        {
                            checked = true;
                        }
                    }
                    if(!checked)
                    {
                        errors.push(elems[i][2]);
                    }
                break;
                case "chain":
                    valid = 0;
                    for(var j in elems[i][2])
                    {
                        err = validate(new Array(elems[i][2][j]));
                        if(!err.length)
                        {
                            valid ++;
                        }
                    }
                    if(valid < elems[i][1])
                    {
                        errors.push(elems[i][3]);
                    }
                break;
            }
        }
        return errors;
    }
    
    function validate_contact_form()
    {
        var elems = new Array();
        elems["name"]    = new Array("text", 3, "name", "name");
        elems["email"]   = new Array("email", "email", "email");
        elems["subject"] = new Array("text", 3, "subject", "subject");
        elems["message"] = new Array("text", 10, "message", "message");
        
        var errors = validate(elems);
        
        if(errors.length)
        {
            alert("forgot something? please complete the following fields:\n\n" + errors.join("\n"));
            return false;
        }
         else
        {
            return true;
        }
    }