function checkEmail(emailadres) {
    if (/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(emailadres)) {
      return (true)
    } 
    return (false)
  }

	function checkValues(form) {
	  var meldingen     = '';

		for(i=0; i<velden_array.length; i++) {
			hetveld = velden_array[i];
      try {
        eval('evalformulier = this.document.forms[\"formulier\"].'+hetveld+'');
      } catch(e) {
        alert(hetveld+' bestaat niet');
      }
      
      if(0) {
      	//alert(evalformulier.type);
      } else {
  			if(evalformulier.value == '') {
  			  meldingen 	  += 'fout';
   			  evalformulier.style.backgroundColor = 'red';
  			} 
  
        if(evalformulier.value != '' || (hetveld == 'emailadres' && checkEmail(evalformulier.value))) {
    			  meldingen 	  += '';
   			    evalformulier.style.backgroundColor = 'white';
  			}
  
        if(hetveld == 'emailadres' && !checkEmail(evalformulier.value)) {
  			  meldingen += 'fout';
   			  evalformulier.style.backgroundColor = 'red';        
          alert('Het emailadres is niet geldig.')
        } 
      }
		}

		if(meldingen != '') {
      alert('U dient alle verplichte velden in te vullen.');
 		} else {
      this.document.forms["formulier"].submit();
    }
	}