es6 promise 面试题

写出下面结果

 const promise = new Promise((resolve, reject) => {
            console.log(1)
            resolve()
            console.log(2)
        })
        promise.then(() => {
            console.log(3)
        })
        console.log(4)
        // 答案：1243

let a = () => {
           console.log(1)
       }
       let b = () => {
           console.log(2)
       }
       function fn() {
           a()
           setTimeout(() => {
               b()
           }, 0);
           console.log(3)
       }
       fn() // 132