String.prototype.leftTrim = function () {
    return (this.replace(/^\s+/,""));
  };
  String.prototype.rightTrim = function () {
    return (this.replace(/\s+$/,""));
  };
//kombiniert "leftTrim" und "rightTrim";
  String.prototype.basicTrim = function () {
    return (this.replace(/\s+$/,"").replace(/^\s+/,""));
  };
//dampft leerzeichen(-sequenzen) innerhalb einer zeichenkette auf ein einzelnes "space" ein;
  String.prototype.superTrim = function () {
    return(this.replace(/\s+/g," ").replace(/\s+$/,"").replace(/^\s+/,""));
  };
/**/
//zugabe: entfernt alle leerzeichen aus einer zeichenkette;
  String.prototype.removeWhiteSpaces = function () {
    return (this.replace(/\s+/g,""));
  };

function setPresentationField() {
	if(document.getElementById('session_id').value == '1') {
		document.getElementById('preferred_oral').disabled = true;
		document.getElementById('preferred_oral').checked = false;
	}
	else {
		document.getElementById('preferred_oral').disabled = false;
	}
}
function setField(id, text) {
	document.getElementById(id).value = text;
}


function setFields(fields) {
	for (var i=0; i < fields.length; i++) {
		document.getElementById(fields[i][0]).value = fields[i][1];
	}
}

function switchTopic(topic) {
	
	// split topics string into array
	var topics = document.getElementById('topics_string').value.split(';');
	
	// delete first elemet if empty
	if (topics[0] == '') {
		topics.shift();
	}
	
	var new_topics = new Array();
	
	var found = 0;
	
	
	for (var i = 0; i < topics.length; i++) {
		
		// trim spaces in front and end of element
		topics[i] = topics[i].basicTrim();
		
		if (topics[i] == topic) {
			found = 1;
		}
		else {
			new_topics.push(topics[i]);
		}
	}
	
	
	if (found == 0) {
		new_topics.push(topic);
	}
	
	
	document.getElementById('topics_string').value = new_topics.join('; ');
}