Question

我正在尝试在我的节点应用程序中创建两个异步承诺，以便在从外部API获取时返回所有最新的部署日期。我之前没有承诺这样做，但是我无法将所有最新的DeploymentDate都返回到映射数组，因为它超出了范围。因此，我遵循谷歌上发现的JavaScript promises教程，但是我没有成功实现它。请在下面找到代码和堆栈跟踪：

const express = require('express')();
const request = require('request');
const moment = require('moment');
const ta = require('time-ago')();
var promise = require('promise')()

const webApplications = require('./account.json');
var newArr = new Array();


express.listen(3001, function() {

  console.log('Server is listening...');
  express.get('/data', function(req, res) {
    res.json(webApplications.map((item, latestDeploymentDate) => {
      res.setHeader('Access-Control-Allow-Origin', '*');
      res.setHeader('Access-Control-Allow-Headers', true);
        // return 'foo';
      const newRelicRequest = {
        url: `https://XXX`,
        headers: {
          'X-Api-Key': 'XXX'
        }
      }
      const gitlabRequest = {
        url: `XXX`,
        headers: {
          'PRIVATE-TOKEN': 'XXX'
        }
      }
      var promise = new Promise(function(resolve, reject) {
        request(newRelicRequest,(err, resp, body) => {
          const data = JSON.parse(body);
          const latestDeployment = data.deployments[0];
          latestDeploymentDate = new Date(latestDeployment.timestamp);
          console.log(new Date(latestDeployment.timestamp));
          resolve(body);
      });

        var secondaryPromise = new Promise(function(resolve, reject) {
          request(gitlabRequest, (err, resp, body) => {
            const gitlabData = JSON.parse(body);
            const currentTag = latestDeployment.description;
            var currentIndex;

        console.log(`${item.appName}` + ' ');
        console.log(`Last deployed: ${latestDeployment.description}
          on ${moment(latestDeploymentDate).format('YYYY-MM-DD')}`);

          gitlabData.find((item, index) => {
            currentIndex = index;
            return item.name == currentTag
          });
          if (currentIndex > 3) {
            console.log(`This ${currentIndex} was released ${ta.ago(latestDeploymentDate)}`);
            resolve(latestDeploymentDate);
          } else {
${ta.ago(latestDeploymentDate)}`);
                console.log(`This ${currentIndex} was released ${ta.ago(latestDeploymentDate)}`);
                resolve(latestDeploymentDate);
              }
            })
            })
            promise.then(function(result){
            console.log(result)
            })
          });
        }));
      });
    })

Answer 1

当您想以可预测的顺序执行另一个承诺时，您希望将它们链接起来：

promise()
|-----------------|
                  secondarypromise(promiseResult)
                  |------------------|
                                     finalHandler(secondayPromiseResult)
                                     |------------------|

在您的代码中，您可以这样做：

promise()
    .then(secondaryPromise) 
    .then(finalHandler);

注意：我发现您使用的request不支持Promises。我可以推荐request-promise - 这样您只需要一个库用于API调用。 request-promise就像request一样，但它基于Promises API实现了所有内容。

多个承诺错误（必须通过新承诺构建承诺）

1 个答案: