ES6 Promise基础用法与代码示例

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
</head>
<body>
<script>
var a=0
var test=function(resolve, reject){
  setTimeout(function(){
    a=4;
    console.log(a)
    if(a<2){resolve('200 OK');}
    if(a>2){reject('400 died');}
  },3000)
}
var p1=new Promise(test);
p1.then(function(resolve){
  console.log(resolve)
},function(reject){
  console.log(reject);
})
</script>
</body>
</html>