The documentation is available online:

  http://nginx.org/en/docs/njs_about.html
  http://nginx.org/en/docs/http/ngx_http_js_module.html
  http://nginx.org/en/docs/stream/ngx_stream_js_module.html

Please report your experiences to the NGINX development mailing list
nginx-devel@nginx.org (http://mailman.nginx.org/mailman/listinfo/nginx-devel).

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