(Vue 3 Composables) JavaScript version of EventBus from a developit/mitt TypeScript library

gistfile1.txt

// JavaScript Version of: https://raw.githubusercontent.com/developit/mitt/main/src/index.ts
// Define the event bus outside of the exported function to ensure a singleton
const all = new Map();

const on = (type, handler) => {
  const handlers = all.get(type) || [];
  all.set(type, [...handlers, handler]);
};

const off = (type, handler) => {
  const handlers = all.get(type) || [];
  if (handler) {
    const index = handlers.indexOf(handler);
    if (index > -1) {
      handlers.splice(index, 1);
      all.set(type, handlers);
    }
  } else {
    all.delete(type);
  }
};

const emit = (type, evt) => {
  const handlers = all.get(type) || [];
  handlers.forEach(handler => handler(evt));

  // Handle wildcard '*' event listeners if any
  const wildcardHandlers = all.get('*') || [];
  wildcardHandlers.forEach(handler => handler(type, evt));
};

// The exported function always returns the same instance of the event bus methods
export const useEventBus = () => ({ on, off, emit });