[SOLVED] node.js i18n: "ReferenceError: __ is not defined"

Issue

Throughout my app I use i18n without problem. However, for email send through a cron job, I get the error:

ReferenceError: __ is not defined

In app.js I configure i18n:

const i18n = require("i18n");
i18n.configure({
    locales: ["en"],
    register: global,
    directory: path.join(__dirname, "locales"),
    defaultLocale: "en",
    objectNotation: true,
    updateFiles: false,
});
app.use(i18n.init);

Throughout my app I use it as __('authentication.flashes.not-logged-in'), like I said without problems. In a mail controller, that is called upon by a cron job, I use it in the same way: __('mailers.buttons.upgrade-now'). However there, and only there, it produces the mentioned error.

Just to try, I've changed this in the mail controller to i18n.__('authentication.flashes.not-logged-in'). But then I get another error:

(node:11058) UnhandledPromiseRejectionWarning: TypeError: logWarnFn is not a function
    at logWarn (/data/web/my_app/node_modules/i18n/i18n.js:1180:5)

Any idea how to make the emails work that are sent through a cron job?

Solution

In comments, the asker clarified that the cron job calls mailController.executeCrons() directly, instead of making an HTTP request to the app. Because of this, the i18n global object never gets defined, because the app setup code in app.js isn't run.

The best solution would be to use i18n's instance usage. You could separate the instantiation and configuration of an I18N object out into a separate function, then call it both in app.js to set it up as Express middleware, and in the mailController.executeCrons() function to use it when being called through the cronjob.

Code outline:

i18n.js (new file)

const i18n = require("i18n");

// factory function for centralizing config;
// either register i18n for global use in handling HTTP requests,
// or register it as `i18nObj` for local CLI use
const configureI18n = (isGlobal) => {
  let i18nObj = {};

  i18n.configure({
    locales: ["en"],
    register: isGlobal ? global : i18nObj,
    directory: path.join(__dirname, "locales"),
    defaultLocale: "en",
    objectNotation: true,
    updateFiles: false,
  });

  return [i18n, i18nObj];
};


module.exports = configureI18n;

app.js

const configureI18n = require('./path/to/i18n.js');

const [i18n, _] = configureI18n(true);
app.use(i18n.init);

mailController.js

const configureI18n = require('./path/to/i18n.js');

const [_, i18nObj] = configureI18n(false);

executeCrons() {
  i18nObj.__('authentication.flashes.not-logged-in');
}

Answered By - DylanSp