Javascript referencing values inside the object it self

Question

I have a config file for my Node.js application which looks like this:

// Development specific configuration
// ==================================
module.exports = {

....

  ip: "localhost",
  //Rabbit MQ
  rabbitmq: {
    username: 'foo',
    password: 'bar',
    ip: 'amqp://'+this.username+':'+this.password+'@rabbitmq',
    queues: {
      name: 'foo'
    }
  }, 
....

};

Here is what the module looks like where I use this config file:

var config = require ('../../config/environment');
this.con = amqp.connect (config.rabbitmq.ip);

I am getting undefined for the username and password:

amqp://undefined:undefined@rabbitmq

I have tried multiple ways such as:

Creating getter functions inside the object like this:

rabbitmq: {
username: 'foo',
password: 'bar',
getUsername: function (){
   return this.username;
},
getpassword: function (){
   return this.password;
},
ip: 'amqp://'+this.getUsername()+':'+this.getpassword()+'@rabbitmq',

Created a self value and assign 'this' and reference it:

self: this,
...
ip: 'amqp://'+self.rabbitmq.username+':'+self.rabbitmq.password+'@rabbitmq',

..

I cannot get the scope to properly work. Am I missing something basic? How can I make this happen? Please help.

Can you try this ip: 'amqp://'+username+':'+password+'@rabbitmq', — Sailesh Babu Doppalapudi, Apr 19 '17 at 02:36
ip: 'amqp://'+username+':'+password+'@rabbitmq', ^ ReferenceError: username is not defined — TitaniuM, Apr 19 '17 at 03:06
Being a part of an expression - `this` holds the value of the current scope you're running at. So what you want to do is not possible (and is not necessary to be honest). — zerkms, Apr 19 '17 at 03:15
Possible duplicate of [Self-references in object literal declarations](http://stackoverflow.com/questions/4616202/self-references-in-object-literal-declarations) — t.niese, Apr 19 '17 at 06:25

score 0 · Answer 1 · edited Apr 19 '17 at 03:14

0

This will work:

var username = 'foo';
var password = 'bar';

module.exports = {
  ip: "localhost",
  //Rabbit MQ
  rabbitmq: {
    username: username,
    password: password,
    ip: 'amqp://'+username+':'+password+'@rabbitmq',
    queues: {
      name: 'foo'
    }
  }
};

edited Apr 19 '17 at 03:14

zerkms

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answered Apr 19 '17 at 03:06

Jake Lampack

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score 0 · Accepted Answer · answered Apr 19 '17 at 06:20

You can do something like this:

var config = {
    ip : "localhost", //Rabbit MQ
    rabbitmq : {
        username : 'foo',
        password : 'bar',
        queues : {
            name : 'foo'
        }
    }
};

config is now declared in module scope so you can reuse its values

config.rabbitmq.ip = 'amqp://' + config.rabbitmq.username + ':' + config.rabbitmq.password + '@rabbitmq';
module.exports = config;

Javascript referencing values inside the object it self

2 Answers2