How to check the installed version of React-Native

You can also open your package.json file in node_modules -> react-native.

The version is at the top:

 {
  "name": "react-native",
  "version": "0.12.0",
  ...
 }

To see what version you have on your Mac(Window also can run that code.), run react-native -v and you should get something like this:

If you want to know what version your project is running, look in /node_modules/react-native/package.json and look for the version key:

The best practice for checking the react native environment information.

react-native info

which will give the information

React Native Environment Info:
System:
  OS: Linux 4.15 Ubuntu 18.04.1 LTS (Bionic Beaver)
  CPU: (8) x64 Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
  Memory: 2.08 GB / 7.67 GB
  Shell: 4.4.19 - /bin/bash
Binaries:
  Node: 8.10.0 - /usr/bin/node
  Yarn: 1.12.3 - /usr/bin/yarn
  npm: 3.5.2 - /usr/bin/npm
npmPackages:
  react: 16.4.1 => 16.4.1 
  react-native: 0.56.0 => 0.56.0 
npmGlobalPackages:
  react-native-cli: 2.0.1
  react-native: 0.57.8