宏任务微任务

考察事件循环、任务队列、和setTimeout、Promise结合，以输出结果顺序的方式来考察

范例 出处

setTimeout(() => console.log(1), 0);
 
new Promise(resolve => {
 console.log(2);
 resolve();
}).then(() => {
  console.log(3);
});
 
console.log(4);

范例 出处

setTimeout(()=> console.log(1))
 
new Promise(resolve => {
  resolve()
  console.log(2)
}).then(_ => {
  console.log(3)
  Promise.resolve().then(_ => {
    console.log(4)
  }).then(_ => {
    Promise.resolve().then(_ => {
      console.log(5)
    })
  })
})
 
console.log(6)

范例 出处

const p = new Promise((resolve, reject) => {
    console.log(1);
    setTimeout(() => {
        console.log(2);
    })
    resolve(1);
}).then(res => {
    console.log(3);
})
 
setTimeout(() => {
    console.log(4);
})
 
console.log(5);

范例 来自面经 第5题

async function async1(){
    console.log('async1 start')
    await async2()
    console.log('async1 end')
}
 
async function async2(){
    console.log('async2')
}
 
console.log('script start')
 
setTimeout(function(){
    console.log('setTimeout')
},0)
 
async1()
 
new Promise(function(resolve){
    console.log('promise1');
    resolve()
}).then(function(){
    console.log('promise2')
})
 
console.log('script end')

范例 来自面经

const pro = new Promise((resolve, reject) => {
  const innerpro = new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(1);
    }, 0);
    console.log(2);
    resolve(3);
  });
  innerpro.then(res => console.log(res));
  resolve(4);
  console.log("pro");
})
pro.then(res => console.log(res));
console.log("end"); ​

范例 来自这里

console.log('begin')
setTimeout(() => {
    console.log('setTimeout 1')
    Promise.resolve().then(() => {
        console.log('promise 1')
        setTimeout(() => {
            console.log('setTimeout2 between promise1&2')
        })
    }).then(() => {
        console.log('promise 2')
    })
}, 0)
console.log('end')

范例 题目出处

function arr(){
    setTimeout(function(){     
        console.log('1');   
    },0)   
    async function async1(){    
        console.log('4');    
        await async2();    
        console.log('6');   
    }   
    async function async2(){    
        console.log('5');   
    }   
    async1();   
    new Promise(function(resolve,reject){    
        console.log('2');    
        resolve();   
    }).then(function(e2){    
        console.log('h');   
    })   
    console.log('3');  
}
arr()

范例5 题目出处

setTimeout(_ => console.log(1))
new Promise(resolve => {
  resolve()
  console.log(2)
}).then(_ => {
  setTimeout(_ => console.log(3))
  console.log(4)
  Promise.resolve().then(_ => {
    console.log(5)
  }).then(_ => {
    Promise.resolve().then(_ => {
      console.log(6)
    })
  })
})
console.log(7)

范例 题目出处

console.log(1);
setTimeout(() => {
 console.log(2);
 Promise.resolve().then(() => {
  console.log(3)
 });
});
new Promise((resolve, reject) => {
 console.log(4)
 resolve()
}).then(() => {
 console.log(5);
})
setTimeout(() => {
 console.log(6);
})
console.log(7);

范例 题目出处

setTimeout(() => {             
  console.log(1)         
}, 0);         
new Promise((res)=>{
  console.log(2);res()
}).then(()=>{
  console.log(4)
})         
console.log(3)

范例 题目出处

const a = () => {     
  new Promise((resolve) => {         
resolve(1)         
console.log('a')     
  }).then(() => {         
console.log('b')     
  }) 
} 
a() 
console.log('c')

范例 题目出处

new Promise((resolve, reject) => {     
  reject(1) 
}).catch(() => {     
  console.log(2); 
}).then(() => {     
  console.log(3) 
}, (v) => { 
  console.log(v) 
}) 
console.log(4)

范例 题目出处

async function async1() {
  console.log('async1 start');
  await async2();
  console.log('async1 end');
}
async function async2() {
  console.log('async2 start');
  return new Promise((resolve, reject) => {
 resolve();
 console.log('async2 promise');
  })
}
console.log('script start');
setTimeout(function() {
  console.log('setTimeout');
}, 0);  
async1();
new Promise(function(resolve) {
  console.log('promise1');
  resolve();
}).then(function() {
  console.log('promise2');
}).then(function() {
  console.log('promise3');
});
console.log('script end')

范例

function app() {
      setTimeout(() => {
        console.log("1-1");
        Promise.resolve().then(() => {
          console.log("2-1");
        });
      });
      console.log("1-2");
      Promise.resolve().then(() => {
        console.log("1-3");
        setTimeout(() => {
          console.log("3-1");
        });
      });
    }
    app();