webextension-rpc/example

import {
  RpcClient,
  RpcServer,
  injectRpcInfo,
} from 'webextension-rpc';
// Only import the *types* of the remote script’s functions.
import type { backgroundScriptRpcServer } from './background-script';

// From background to content script.
const contentScriptRpcServer = new RpcServer({
  async setColour(colour: string) {
    document.body.style.backgroundColor = colour;
  },
});
export type { contentScriptRpcServer }

// From content to background script.
const duplicateMe = new RpcClient<typeof backgroundScriptRpcServer>().func('duplicateTab');
// The injectRpcInfo placeholder will be replaced by actual info.
const newTabId = await duplicateMe(injectRpcInfo, true);