Promiseは両目がぼんやりしていますから、両目が輝いています.(3)-Promiseのいくつかの重要な問題(一)

    promise   ?  
promise          ,   pending,revolved(    fulfilled),rejected  ,  
   resolve(value) ,    pending  resolved  
   reject(reason)    Error ,    pending  rejected  
**  **:   promise         ,              ,             

const p = new Promise((resolve, reject) => {  
  // resolve(1) // promise  resolved       
 // reject(2) // promise  rejected      
 // throw new Error('   ') //     , promise  rejected    , reason    error  
 throw 3 //     , promse  rejected    , reason    3  
})  
p.then(  
  value => {  
    console.log('value1', value)  
  },  
  reason => {  
    console.log('reason1', reason)  
  }  
)  
  
p.then(  
  value => {  
    console.log('value2', value)  
  },  
  reason => {  
    console.log('reason2', reason)  
  }  
)  
  
p.then(  
  value => {  
    console.log('value3', value)  
  },  
  reason => {  
    console.log('reason3', reason)  
  }  
)

  promise             ?  
1.     ,                 ,                
2.            ?  
  1).  executor     resolve()/reject() 
  2).          then()
3.           ?  
  1).         ,          ,         ,      
  2).         ,        ,         ,     
    

//   :        ,         
new Promise((resolve, reject) => {  
  setTimeout(() => {  
    //1         
  resolve(1) //       (      ),           
  }, 1000);  
}).then(//        ,              
  value => {  
    console.log('value', value)  
  },  
  reason => {  
    console.log('reason', reason)  
  }  
)  
  
//     ,          
new Promise((resolve, reject) => {  
  //       (      )  
  resolve(1)  
}).then(  
  //        ,           
  value => {  
    console.log('value2', value)  
  },  
  reason => {  
    console.log('reason2', reason)  
  }  
)  
  
console.log('-------')  

//     ,            
const p = new Promise((resolve, reject) => {  
  setTimeout(() => {  
    resolve(1)  
  }, 1000);  
})  
  
setTimeout(() => {  
  p.then(  
    value => {  
      console.log('value3', value)  
    },  
    reason => {  
      console.log('reason3', reason)  
    }  
  )  
}, 2000);

promise.then()    promise          ?  
1.     :  then()                
2.     :  
  1).       ,  promise  rejected, reason       
  2).        promise    ,  promise  resolved, value      
  3).           promise,  promise        promise   
  

new Promise((resolve, reject) => {  
  resolve(1)  
  // reject(1)  
}).then(  
  value => {  
    console.log('onResolved1()', value)  
    // return 2  
    // return Promise.resolve(3) 
    // return Promise.reject(4) 
    // throw 5  
    },  
  reason => {  
    console.log('onRejected1()', reason)  
    // return 2  
    // return Promise.resolve(3) 
    // return Promise.reject(4)  
    throw 5  
  }  
).then(  
  value => {  
    console.log('onResolved2()', value)  
  },  
  reason => {  
    console.log('onRejected2()', reason)  
  }  
)

       ,        :
onResolved1() 1
onResolved2() undefined
  :   resolve(1) ,  promise     resolved,       .then onResolved  ,       1.
  console.log()       undefined,undefined    Error Promise  ,        .then() onResolved  ,  undefined