Note: only the asynchronous API is supported, due to the limitations of having to go over the RCTBridge, and there being no secure RNG in JavaScriptCore (Math.random is a bit of a joke in the industry)

var randomBytes = require('react-native-randombytes')
randomBytes(4, (err, bytes) => {
  console.log(bytes.toString('hex'))
})

Installation

`iOS`

Drag RNRandomBytes.xcodeproj from node_modules/react-native-randombytes into your XCode project.
Click on the project in XCode, go to Build Phases, then Link Binary With Libraries and add libRNRandomBytes.a

Confused? See an example with screenshots here