player/js/utils/expressions/TextInterface.js

var TextExpressionInterface = (function(){
	return function(elem){
        var _prevValue, _sourceText;
        function _thisLayerFunction(){
        }
        Object.defineProperty(_thisLayerFunction, "sourceText", {
            get: function(){
                var stringValue = elem.textProperty.currentData.t;
                if(stringValue !== _prevValue) {
                    elem.textProperty.currentData.t = _prevValue;
                    _sourceText = new String(stringValue);
                    //If stringValue is an empty string, eval returns undefined, so it has to be returned as a String primitive
                    _sourceText.value = stringValue ? stringValue : new String(stringValue);
                }
                return _sourceText;
            }
        });
        return _thisLayerFunction;
    };
}());