<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<div></div>
</body>
<script>
var a=1
var b=0
console.log(a) //a=1
console.log(a++) //a=1
console.log(a) //a=2
console.log(a+b) //a+b=2
</script>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<div></div>
</body>
<script>
var a=1
var b=0
console.log(a) //a=1
console.log(a++) //a=1
console.log(a) //a=2
console.log(a+b) //a+b=2
</script>
</html>
当执行完a++之后,在本行a的值没有发生变化,但是如果继续运行的时候,并且进行计算那么a的值就会产生变化,并且计算时用的是变化的值。