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生成器和promise 的结合

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<!DOCTYPE html>
<html>
	<head>
		<title>Combining generators and promises</title>
		<meta charset="utf-8">
		<link rel="stylesheet" href="../assert.css">
		<script src="../assert.js"></script>
		<script src="getJSON.js"></script>
		<script>
		 "use strict"
			async(function*(){
			  try {
			    const ninjas = yield getJSON("data/ninjas.json");
			    const missions = yield getJSON(ninjas[0].missionsUrl);
			    const missionDescription = yield getJSON(missions[0].detailsUrl);

				assert(ninjas !== null && missions !== null 
					&& missionDescription !== null, 
					"All ready!");
			  }
			  catch(e) {
				fail("We weren't able to get mission details");
			  }
			});

			function async(generator) {
				const iterator = generator();

				function handle(iteratorResult) {
			    	if(iteratorResult.done) { return; }

			    	const iteratorValue = iteratorResult.value;

			    	if(iteratorValue instanceof Promise) {
						iteratorValue.then(res => handle(iterator.next(res)))
									 .catch(err => iterator.throw(err))
			    	}
				}

				try {
			    	handle(iterator.next());
			  	}
			  	catch (e) { iterator.throw(e); }
			}
		</script>
	</head>
	<body>Has to be run on a server (e.g MAMP or WAMP)</body>
</html>