Another problem that JavaScript professionals have experienced over the years is the lack of a module system in the language. Initially, the community developed different patterns, aiming to enforce the modularity and the encapsulation of the software we produce. Such patterns included the module pattern, which takes advantage of the functional lexical scope and closures. Another example is the namespace pattern, which represents the different namespaces as nested objects. AngularJS introduced its own module system that unfortunately doesn't provide features, such as lazy module loading. However, these patterns were more like workarounds rather than real solutions.

CommonJS (used in node.js) and AMD (Asynchronous Module Definition) were later invented. They are still widely used today and provide features such as handling of circular dependencies, asynchronous module loading (in AMD), and so on.

TC39 took the best of the existing module systems and introduced...