SOURCE

//将异步包装成一个promise
new Promise(function(resolve,reject){
    setTimeout(function(){
        resolve(1);
    },2000)
    console.log('promise init');
}).then(res => {
    console.log(res);
});
console.log('window');

var promise = new Promise(function (resolve){
    console.log("inner promise"); // 1
    resolve(42);
});
promise.then(function(value){
    console.log(value); // 3
});
console.log("outer promise"); // 2