Promise両目がぼんやりしてから両目が光るまで(4)-Promiseのいくつかの肝心な問題(二)

promise then()      promise,   then           /    

new Promise((resolve, reject) => {  
  setTimeout(() => {  
    console.log("    1(  )")  
    resolve(1)  
  }, 1000);  
}).then(  
  value => {  
    console.log('  1   : ', value)  
    console.log('    2(  )')  
    return 2  
  }  
).then(  
  value => {  
    console.log('  2   :', value)  
  
    return new Promise((resolve, reject) => {  
      //     3(  )  
  setTimeout(() => {  
        console.log('    3(  ))')  
        resolve(3)  
      }, 1000);  
    })  
  }  
).then(  
  value => {  
    console.log('  3   : ', value)  
  }  
)

    :
1  
    1(  )
  1   :  1
    2(  )
  2   : 2
  1  
    3(  ))
  3   :  3

1.    promise then     ,             ,  
2.           ,               

new Promise((resolve, reject) => {  
  // resolve(1)  
  reject(1)  
}).then(  
  value => {  
    console.log('onResolved1()', value)  
    return 2  
  },  
  // reason => {throw reason}  //    reject  ,         
).then(  
  value => {  
    console.log('onResolved2()', value)  
    return 3  
  },  
  // reason => {throw reason}  //    reject  ,         
).then(  
  value => {  
    console.log('onResolved3()', value)  
  },  
  // reason => Promise.reject(reason)  //    reject  ,         
).catch(reason => {  
  console.log('onReejected1()', reason)  
  // throw reason  
 // return Promise.reject(reason)
 }).then(  
  value => {  
    console.log('onResolved3()', value)  
  },  
  reason => {  
    console.log('onReejected2()', reason)  
  }  
)

    :
onReejected1() 1
onResolved3() undefined

  promise ?  
1.    promise then     ,      ,              
2.   :           pending   promise  

new Promise((resolve, reject) => {  
  resolve(1)  
}).then(  
  value => {  
    console.log('onResolved1()', value)  
    return new Promise(() => {}) //     pending promise    promise   
  },  
).then(  //        
  value => {  
    console.log('onResolved2()', value)  
  },  
  reason => {  
    console.log('onResolved2()', reason)  
  },  
)

    :
onResolved1() 1