专题 | 同步异步

1.


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
		console.log(1);
		console.log(2);
		console.log(3);
		</script>
	</body>
</html>

2


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
		console.log(1);
		setTimeout(function(){
			console.log(2);
		},1000)
		console.log(3);
		</script>
	</body>
</html>

3.


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
		console.log(1);
		setTimeout(function(){
			console.log(4);
		},0)
		console.log(3);
		</script>
	</body>
</html>

4.


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
	console.log(1);
	setTimeout(function(){
		console.log(2);
	},3000)
	setTimeout(function(){
		console.log(3);
	},1000)
		</script>
	</body>
</html>

5.


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
console.log('1');
setTimeout(function () {
  console.log('2');
  new Promise(function(resolve, reject) {
    console.log('promise-start2');
    resolve();
  }).then(function() {
    console.log('promise-end2');
 });
},0);
new Promise(function(resolve, reject) {
    console.log('promise-start');
    resolve();
}).then(function() {
    console.log('promise-end');
});
setTimeout(function () {
    console.log('3');
},0);
console.log('4');
		</script>
	</body>
</html>

还是不懂promise的目的

6.这个经典,随便换着位置理解


<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
        console.log('1');
        new Promise(function(resolve, reject) {
           console.log('promise-start2');
		   // setTimeout(function () {
		   //        console.log('6');
		   // },0);
           resolve();
        }).then(function() {
			setTimeout(function () {
			       console.log('3');
			},0);
          console.log('promise-end2');
		 
        });
      
        console.log('4');
		</script>
	</body>
</html>

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原文地址：https://blog.csdn.net/A123ppleQueen/article/details/125537460

专题 | 同步 异步

1.

2

3.

4.

5.

6.这个经典,随便换着位置理解

专题 | 同步异步