njs scripting language

njs is a subset of the JavaScript language that allows extending nginx functionality. njs is created in compliance with ECMAScript 5.1 (strict mode) with some ECMAScript 6 and later extensions. The compliance is still evolving.

• Download and install
• Changes
• Reference
• Examples
• Compatibility
• Command-line interface

• ngx_http_js_module
• ngx_stream_js_module

Use cases

• Complex access control and security checks in njs before a request reaches an upstream server
• Manipulating response headers
• Writing flexible asynchronous content handlers and filters

See examples and blog posts for more njs use cases.

Basic HTTP Example

To use njs in nginx:

• install njs scripting language

• create an njs script file, for example, hello_world.js. See Reference for the list of njs properties and methods.

  function hello(r) {
      r.return(200, "Hello world!");
  }
  

• in the nginx.conf file, enable ngx_http_js_module module and specify the js_include directive with the hello_world.js script file:

  load_module modules/ngx_http_js_module.so;
  
  events {}
  
  http {
      js_include hello_world.js;
  
      server {
          listen 8000;
  
          location / {
              js_content hello;
          }
      }
  }
  
  

There is also a standalone command line utility that can be used independently of nginx for njs development and debugging.

Presentation at nginx.conf 2018