Lots of JavaScript projects use a dozen of various frameworks, libraries, and third-party scripts. More often code which you produce largely depends from vendors’ work. The good example is jQuery and Lodash libraries which are involved in our pretty code. They are designed to facilitate the work and they are the remedy for especially commonly used, repeatable pieces of code.
This kind of libraries (and frameworks) provide an another abstraction layer behind our code making the execution process more complex. It’s invisible until you’ll need to debug your code because of errors.