A postImportTableFunction can be defined

gtfs.js

@@ -170,6 +170,12 @@ class Gtfs {
    *
    * Optional ad-hoc boolean. Default is true. Will force the parser to ignore invalid rows in the tables.
    *
+   *
+   * # options.postImportTableFunction
+   *
+   * Optional ad-hoc function which will be applied on every item of every table after importation.
+   *
+   *
    * # options.forcedSchema
    *
    * Will overwrite the default schema by the value passed.
@@ -179,6 +185,7 @@ class Gtfs {
    * @param {{
    *   regexPatternObjectsByTableName: Map.<string, Array.<{regex: RegExp, pattern: string}>>,
    *   throws: boolean,
+   *   postImportTableFunction: function,
    *   forcedSchema,
    * }} [options] Optional. See list above.
    * @return {Gtfs} gtfs Instanciated GTFS object.

helpers/import.js

@@ -24,12 +24,15 @@ exports.importTable = (gtfs, tableName) => {
     const rows = getRows(fileContent, gtfs._regexPatternObjectsByTableName.get(tableName), tableName);
 
     gtfs._tables.set(tableName, processRows(gtfs, tableName, indexKeys, rows, gtfs._shouldThrow));
-    return;
-  }
+  } else {
+    infoLog(`Empty table will be set for table ${tableName} (no input file at path ${gtfs._path}).`);
 
-  infoLog(`Empty table will be set for table ${tableName} (no input file at path ${gtfs._path}).`);
+    gtfs._tables.set(tableName, new Map());
+  }
 
-  gtfs._tables.set(tableName, new Map());
+  if (gtfs._postImportTableFunction) {
+    gtfs.forEachItemInTable(tableName, gtfs._postImportTableFunction);
+  }
 };
 
 /**