如何在使用Promise的节点中编写同步功能

Question

1.如何在节点中同步写入Promises，以便获得所需的输出。我是一个新手，并会感谢任何帮助/建议。

// This is my core function 

var compareData = function(userIdArray) { 
    return new Promise(function(resolve, reject) { 
    var missingArray = new Array(); 
    userIdArray.forEach(function(id) { 
     var options = { 
     method: 'POST', 
     url: 'http://localhost:6006/test1', 
     headers:{ 
     'content-type': 'application/json' }, 
      body: { email: id }, 
      json: true 
     }; 

     request(options, function (error, response, body) { 
     missingArray.push(body); 
     }); 
    }); 
    resolve(missingArray); 
    }); 
} 


//I'm calling my function here 

compareData(userIdArray) 
.then(function(missingArray){ 
    console.log("The Body is: "+ missingArray); 
}); 

/* I expect the console.log to print the missingArray with data from my POST call, 
but it prints an empty array. Can someone please tell me how to do this synchronously. 
I'm pretty new to Node and finding it difficult to understand.*/ 

Answer 1

与bluebird和request-promise：

var Promise = require('bluebird'); 
var request = require('request-promise'); 

var compareData = function(userIdArray) { 
    //Promise.all(): 
     //takes an array of promises (and/or values), 
     //returns a promise of the resolved array 
    return Promise.all( 
     userIdArray.map(function(id){ 
      return request({ 
       method: 'POST', 
       url: 'http://localhost:6006/test1', 
       headers: { 'content-type': 'application/json' }, 
       body: { email: id }, 
       json: true 
      }); 
     }) 
    ); 
} 

有什么需要进一步的解释？

Answer 2

没有图书馆，并假设request尚未返回一个承诺

var compareData = function(userIdArray) { 
    return Promise.all(
     userIdArray.map(function(id) { 
      var options = { 
       method : 'POST', 
       url  : 'http://localhost:6006/test1', 
       headers : { 'content-type': 'application/json' }, 
       body : { email: id }, 
       json : true 
      }; 

      return new Promise(function(resolve, reject) { 
       request(options, function(error, response, body) { 
        if (error) { 
         reject(); 
        } else { 
         resolve(body); 
        } 
       }); 
      }); 
     }) 
    ); 
} 

compareData(userIdArray).then(function(missingArray) { 
    console.log(missingArray); 
}); 

Answer 3

如果你不想使用外部库根据@Thomas的回答，您可以直接使用原生的承诺 - 这不是太多冗长

var compareData = function compareData(userIdArray) { 
    return Promise.all(userIdArray.map(function (id) { 
     return new Promise(function (resolve, reject) { 
      var options = { 
       method: 'POST', 
       url: 'http://localhost:6006/test1', 
       headers: { 
        'content-type': 'application/json' 
       }, 
       body: { 
        email: id 
       }, 
       json: true 
      }; 
      return request(options, function (error, response, body) { 
       error ? reject(error) : resolve(body); 
      }); 
     }); 
    })); 
}; 

compareData(userIdArray) 
.then(function (missingArray) { 
    console.log("The Body is: " + missingArray); 
}); 

或者，因为这是节点，它可以处理更多的现代代码：

var compareData = userIdArray => 
    Promise.all(userIdArray.map(id => 
     new Promise((resolve, reject) => 
      request({ 
       method: 'POST', 
       url: 'http://localhost:6006/test1', 
       headers: { 
        'content-type': 'application/json' 
       }, 
       body: { 
        email: id 
       }, 
       json: true 
      }, (error, response, body) => error ? reject(error) : resolve(body)) 
     ) 
    )); 

compareData(userIdArray) 
.then(missingArray => 
    console.log("The Body is: "+ missingArray) 
);