Node.js export variable

Question

I am writing a Node.js module and I need to pass variable data from the main file to the functions. I am doing this:

var region;
var api_key;

exports.region = region;
exports.api_key = api_key;


module.exports = {

  getSummonerId: function(sum, callback) {

    var summoners = {};
    var summoner = sum.replace(/\s+/g, '');

    request("https://na.api.pvp.net/api/lol/" + region + "/v1.4/summoner/by-name/" + summoner + "?api_key=" + api_key, function(error, response, body) {
      summoners[summoner] = JSON.parse(body);
      callback(summoners[summoner][summoner].id);
    });
  }
}

And in the main file:

var lol = require('./apiwrapper.js');

lol.api_key = "example";
lol.region  = "las";


lol.getChampions(function(data) {
  console.log(data);
})

But from apiwrapper.js file, those two variables' value are always "undefined".

How can I fix this?

Please refer this: http://stackoverflow.com/questions/7137397/module-exports-vs-exports-in-nodejs?rq=1 — BlackMamba, Dec 23 '14 at 04:21
You cann't use `exports.region` and `module.exports` at the same time. — BlackMamba, Dec 23 '14 at 04:21

score 13 · Answer 1 · answered Dec 23 '14 at 05:01

The value that is imported to the other module is module.exports. So, what you assign to module.exports is exported. Whatever was assigned earlier to it is lost.

The relation between module.exports and exports is that they refer to the same object initially:

var exports = module.exports = {};

So, assigning a property to either of them mutates the same object. However, you are assigning a new object to module.exports, so now both of them reference different objects.

A simple solution is to assign the new object to exports as well and then assign the other properties:

exports = module.exports = {...};
exports.region = region;

If you want to keep the order of the statements, then you have to extend the default exports object, instead of creating a new one:

Object.assign(exports, { ... });

score 1 · Answer 2 · edited Oct 03 '20 at 23:49

Use:

module.exports = {
  region: my_region,
  api_key: my_api_key,
  getSummonerId: function(sum, callback) {

    var summoners = {};
    var summoner = sum.replace(/\s+/g, '');

    request("https://na.api.pvp.net/api/lol/" + region + "/v1.4/summoner/by-name/" + summoner + "?api_key=" + api_key, function(error, response, body) {
          summoners[summoner] = JSON.parse(body);
          callback(summoners[summoner][summoner].id);
    });
  }
}

In your case, "module.exports" is overwriting the previously exported variables. Which is the reason you are getting undefined for those.

Node.js export variable

2 Answers2