getRuntimeKind

getRuntimeKind allows you to get the kind of the current runtime. It's useful in advanced scenarios, where you need to check the runtime kind before executing certain code paths or where you need to have separate implementations per runtime.

getRuntimeKind is a direct replacement for the deprecated _WORKLET global variable.

Reference

import {
  getRuntimeKind,
  runOnUI,
  createWorkletRuntime,
  runOnRuntime,
} from 'react-native-worklets';

console.log(getRuntimeKind()); // 1 (RN Runtime)

runOnUI(() => {
  console.log(getRuntimeKind()); // 2 (UI Runtime)
})();

runOnRuntime(createWorkletRuntime(), () => {
  console.log(getRuntimeKind()); // 3 (Worker Runtime)
})();

Type definitions

enum RuntimeKind {
  ReactNative = 1,
  UI = 2,
  Worker = 3,
}

function getRuntimeKind(): RuntimeKind;

Returns

An enum value representing the current runtime kind:

• 1 for RN Runtime
• 2 for UI Runtime
• 3 for Worker Runtime

Example

import {
  getRuntimeKind,
  RuntimeKind,
  runOnJS,
  runOnUI,
} from 'react-native-worklets';

function logToConsole(message: string) {
  console.log(message);
}

function log(message: string) {
  'worklet';
  if (getRuntimeKind() === RuntimeKind.ReactNative) {
    console.log(`RN: ${message}`);
  } else {
    // Fun fact - this is how `console.log` is implemented on Worklet Runtimes.
    runOnJS(logToConsole)(`UI: ${message}`);
  }
}

function randomDispatch() {
  if (Math.random() > 0.5) {
    runOnUI(log)('Hello!');
  } else {
    log('Hello!');
  }
}

randomDispatch(); // Could log either "RN: Hello!" or "UI: Hello!"

Optimizations

For micro-optimizations of your code you can skip the invocation of getRuntimeKind and use the global variable __RUNTIME_KIND directly:

import {
  getRuntimeKind,
  runOnUI,
  createWorkletRuntime,
  runOnRuntime,
} from 'react-native-worklets';

console.log(globalThis.__RUNTIME_KIND); // 1 (RN Runtime)

Be aware that accessing the global variable __RUNTIME_KIND before importing anything from react-native-worklets might be undefined. This is because the global variable is set only after the react-native-worklets module is loaded. This is especially important in Web contexts, where additional bundler optimizations may be in place.

Remarks

• If you're using the global variable __RUNTIME_KIND make sure to reference it by accessing the global object, i.e. globalThis.__RUNTIME_KIND to avoid the pitfall where you accidentally reference a local variable with the same name.