The following code cause this error:

<!DOCTYPE html>
<html>

<head>
	<script 
	src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.29/browser.js">
	</script>
	<script type="text/babel">

		const delay = seconds => {
			return new Promise(
				resolve => setTimeout(resolve, seconds * 1000)
			)
		}

		const countToFive = async () => {
			console.log('Zero seconds');
			await delay(1);
			console.log('one second');
			await delay(2);
			console.log('two seconds');
			await delay(5);
			console.log('five seconds');
		}

		countToFive();
	</script>
	<title>Async</title>
</head>

<body>
</body>

</html>

Babel have issues with the package. The babel script must be removed.

<!DOCTYPE html>
<html>

<head>
	<script>

		const delay = seconds => {
			return new Promise(
				resolve => setTimeout(resolve, seconds * 1000)
			)
		};

		const countToFive = async () => {
			console.log('zero seconds');
			await delay(1);
			console.log('one second');
			await delay(1);
			console.log('two seconds');
			await delay(3);
			console.log('five seconds');
		};

		countToFive();

	</script>
	<title>Async</title>
</head>
<body>
</body>
</html>

And the Output should be (in different times):