export default () => { let interval: ReturnType = null; self.onmessage = (message: MessageEvent) => { if(!message) return; const data: { [index: string]: any } = message.data; switch(data.action) { case 'START': interval = setInterval(() => postMessage(null), data.content); break; case 'STOP': if(interval) { clearInterval(interval); interval = null; } break; } }; };