Using ecma6

When I try to compile ecma6 code I get:

Use –language_in=ECMASCRIPT6 or ECMASCRIPT6_STRICT or higher to enable ES6 features.

However I do not know where can I use this, project.py does not accept this cli switch.

Ok I found it. It turned out that blend4web uses the Google Closure Compiler, and the

–language_in

parameter hardcoded in scripts/lib/project_cli.py

— a/scripts/lib/project_cli.py
+++ b/scripts/lib/project_cli.py
@@ -348,7 +348,7 @@ def fill_global_paths(base_dir):
 
     # closure compiler params
     _js_cc_params = [_java_exec, "-jar", js_cc_path,
-                     "–language_in=ECMASCRIPT5"]
+                     "–language_in=ECMASCRIPT6"]
 
     # engine sources directory
     _src_dir = join(base_dir, "src")

However I guess it is not wise to change this parameter, because all of the b4w modules are written in es5. So It can effect their optimization badly. So I will transpile my code to es5.