A package is a bundle of JavaScript files that exposes only specific variables to a Meteor app. Other than in a Meteor app, package files will get loaded in the loading order we specify.
Every package needs a package.js file that contains the configuration of that package. In such a file, we can add a name, description, and version, set the loading order, and determine which variables should be exposed to the app. Additionally, we can specify unit tests for our packages to test them.
An example of a package.js file can look like this:
Package.describe({
name: "mrt:moment",
summary: "Moment.js, a JavaScript date library.",
version: "0.0.1",
git: "https://..."
});
Package.onUse(function (api, where) {
api.export('moment');
api.addFiles('lib/moment-with-langs.min.js', 'client');
});
Package.onTest(function(api){
api.use(["mrt:moment", "tinytest"], ["client", "server"]);
api.addFiles("test/tests.js", ["client", "server"]);
});