Example for using multiple inline web workers

inline-multi-worker.js

const createWorker = (function(){
	let workerId = 0;

	function worker(){
		self.onmessage = function(e){
			const received = new Date()

			const {type, data, created} = e.data 

			switch(e.data.type){
				case 'join':
					const result = data.join('')
					const processed = new Date()
					const processing = processed - received

					return self.postMessage({
						type,
						created, 
						received,
						processed,
						processing,
						result
					})
			}
		}
	}

	const stringWorker = worker.toString();
	const code = stringWorker.substring(stringWorker.indexOf("{")+1, stringWorker.lastIndexOf("}"));

	return function(){
		workerId = workerId + 1;

		let onmessageCallback;

		const blob = new Blob([code], {type: "application/javascript"});
		const worker = new Worker(URL.createObjectURL(blob));

		worker.onmessage = function(e){
			if(onmessageCallback){
				const accepted = new Date()
				onmessageCallback({
					...e.data,
					accepted
				})
			}
		}

		return {
			worker,
			terminate: () => {
				console.log(`terminate`)
				worker.terminate()
			},
			postMessage(type, data){
				worker.postMessage({type, data, created: new Date().getTime()})
			},
			onmessage(callback){
				onmessageCallback = callback
			}
		}
	}
})();


const w1 = createWorker()
const w2 = createWorker()

const logResponse = (name, style) => resp => {
	const messages = [
		`%c ${name} full processing time ${resp.accepted - resp.created}ms.`,
		`%c ${name} calc time ${resp.processing}ms.`,
		`%c ${name} send time ${resp.received - resp.created}ms.`,
		`%c ${name} accept time time ${resp.accepted - resp.processed}ms.`,
		`%c ${name} accepted ${resp.accepted.toString()}`
	];
	messages.forEach(message => {
		console.log(message, style)
	});

	document.getElementById(name).innerHTML = JSON.stringify(messages, null, 2);
}

w1.onmessage(logResponse('W1', 'color: #06c'))
w2.onmessage(logResponse('W2', 'color: green'))

setTimeout(() => {
	w1.terminate()
}, 10)
w1.postMessage('join', new Array(10000000).fill(0))
w2.postMessage('join', new Array(100000).fill(0))

https://jsfiddle.net/785ektw9/24/