任务执行顺序

setImmediate(function(){
    console.log(2)
})
setTimeout(function(){
    console.log(1)
},0)
process.nextTick(()=>{
    console.log(3)
})
new Promise((resovle,reject)=>{
    console.log(4)
    resovle(4)
}).then(function(){
    console.log(5)
})
console.log(6)