Use

can-namespace exports an object that can be used to ensure only one version of a module is loaded in an app.

For example, if you have a module can-unicorn that you want to make sure is only loaded a single time, you can use can-namespace:

import namespace from 'can-namespace';

var unicorn = {
    // ...
};

if (namespace.unicorn) {
    throw new Error("You can’t have two versions of can-unicorn; check your dependencies");
}
export default namespace.unicorn = unicorn;

Any module requiring can-namespace will receive the same module because only one version of can-namespace will ever be published.