JS中級Promise

▼▼▼Promiseの使い道と基本的な使い方

  var a = new Promise();

  a.then(function(){

  }).catch(function(){

  })

  var a = new Promise(function(resolve,reject){
  	success();
  });

  a.then(function(){
	//성공시 실행할 내용
  }).catch(function(){
	//실패시 실행할 내용
  })

▶▼▼承諾の実際の使用例1

var a = new Promise(function(resolve,reject){
 var hardwork = 1 + 1;
  resolve();
})

a.then(function(){
	console.log('calculation success')
}).catch(function(){

});

  var a = new Promise(function(resolve,reject){
   var hardwork = 1 + 1;
    reject();
  })

  a.then(function(){
     
  }).catch(function(){
	 console.log('calculation failed')
  });

  var a = new Promise(function(resolve,reject){
   var hardwork = 1 + 1;
    resolve(hardwork);
  })

  a.then(function(outcome){
	 console.log('calculation success:' + outcome)     
  }).catch(function(){

  });

▶▼▼承諾の実際の使用例2

  var a = new Promise(function(resolve,reject){
	setTimeout(function(){
        resolve();
    }, 1000)
  })

  a.then(function(outcome){
	 console.log('success')     
  }).catch(function(){
	console.log('failed')
  }).finally('good');//성공 여부에 관계없이 무조건 실행시킬 코드

▶▼▼約束のいくつかの特徴

/* 

성공 / 실패 판정 전 -> pending 상태
성공 후 -> fulfilled 상태
실패 후 -> rejected 상태

*/ 

  let a = new Promise(function(resolve, reject){

    setTimeout(function(){
      console.log('promise');
      console.log(a)// pending

      resolve();//성공
      reject();//실패
    })


  }, 1000);

  a.then(function(){
    console.log('resolved')//fulfilled
  }).catch(function(){
    console.log('reject')//rejected
  }).finally(function(){
    console.log('finally')//fulfilled
  })

  let a = new Promise(function(resolve, reject){

    setTimeout(function(){
      오래걸리는연산(); 
      console.log(a)// pending

      resolve();//성공
      reject();//실패
    })


  }, 1000);

  a.then(function(){
    console.log('resolved')//fulfilled
  }).catch(function(){
    console.log('reject')//rejected
  }).finally(function(){
    console.log('finally')//fulfilled
  })

▶️ Promise chaining

// jquery 적용시
var promise1 = new Promise(function(resolve, reject) {
    $.get('https://codingapple1.github.io/hello.txt').done(function(result){
      resolve(result)
    });
});

프로미스.then(function(result) {
  console.log(result);

  var promise2 = new Promise(function(resolve, reject) {
    $.get('https://codingapple1.github.io/hello2.txt').done(function(result){
      resolve(result)
    })
  });

  return promise2;

}).then(function(result) {
    console.log(result);
})