parseValue: function (oValue) {
    if(oValue !== null) {
        return oValue.trim();
    }
    return oValue;
},

trimString : function(oValue) {
    if(oValue !== null) {
        return oValue.trim();
    }
    return oValue;
},

mandatoryValueType : SimpleType.extend("text", {
    formatValue: function (oValue) {
        return oValue;
    },
    parseValue: this.trimString,
    validateValue: function (oValue) {
        if (!oValue) {
            throw new ValidateException(Utils.i18n("MANDATORY_VALIDATE_ERROR"));
        }
    }
}),

var Utils = {
  ...
  trimString: function() {
    ...
  },
  ...
  parseValue: function() {
    this.trimString();
  }
  ..
}