CODEWITHSUNDEEP
javascriptnode.js
user9393908
user9393908

Reputation: 51

Returning nested promises to another function

I have a NodeJS application and I think I have an issue with returning from inside a nested Promise.

As below, the getToken function is working. It calls another function to retrieve a password. After this, it uses the password value when making a GET call.

We then successfully get a token and we print the body to the console. This works.

However, I now have the challenge of passing the value of body which is my token, to another method for later consumption. printBodyValue currently fails and fails with an 'undefined' error.

How can I pass the value from deep inside getToken to printBodyValue

getToken: function() {
   module.exports.readCredentialPassword()
 .then(result => {
     var request = require('request-promise');
     var passwd = result;
     var basicAuthData = "Basic " + (new Buffer("fooUser" + ":" + passwd).toString("base64"));
     var options = {
        method: "GET",
        uri: ("http://localhost:8001/service/verify"),
        followRedirects: true,
        headers: {
          "Authorization": basicAuthData
        }
     };
     return request(options)
       .then(function (body) {
         console.log("Token value is: ", body);
         return body;
       })
       .catch(function (err) {
         console.log("Oops! ", err);
       });
   });
}

printBodyValue: function() {
   module.exports.getToken().then(function(body) {
    console.log("Token value from printBodyValue is: \n", body);
   });
}

Upvotes: 1

Views: 51

Answers (1)

CertainPerformance
CertainPerformance

Reputation: 370619

In getToken, instead of using the nested promise anti-pattern, chain your promises instead, and return the final promise, so that you can then consume the promise and use its resolved value:

(also, since you're using ES6, prefer const over var)

getToken: function() {
  return module.exports.readCredentialPassword()
    .then(result => {
      const request = require('request-promise');
      const passwd = result;
      const basicAuthData = "Basic " + (new Buffer("fooUser" + ":" + passwd).toString("base64"));
      module.exports.log("Sending Request: ", jenkinsCrumbURL);
      const options = {
        method: "GET",
        uri: ("http://localhost:8001/service/verify"),
        followRedirects: true,
        headers: {
          "Authorization": basicAuthData
        }
      };
      return request(options);
    })
    .then(function(body) {
      console.log("Token value is: ", body);
      // the return value below
      // will be the final result of the resolution of
      // `module.exports.readCredentialPassword`, barring errors:
      return body;
    })
    .catch(function(err) {
      console.log("Oops! ", err);
    });
}

printBodyValue: function() {
  module.exports.getToken().then(function(body) {
    console.log("Token value from printBodyValue is: \n", body);
  });
}

Upvotes: 1

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