Mastering JavaScript

Functions, Closures,
and Modules
In the previous chapter, we deliberately did not discuss certain aspects of JavaScript.
These are some of the features of the language that give JavaScript its power and
elegance. If you are an intermediate- or advanced-level JavaScript programmer, you
may be actively using objects and functions. In many cases, however, developers
stumble at these fundamental levels and develop a half-baked or sometimes
wrong understanding of the core JavaScript constructs. There is generally a
very poor understanding of the concept of closures in JavaScript, due to which
many programmers cannot use the functional aspects of JavaScript very well. In
JavaScript, there is a strong interconnection between objects, functions, and closures.
Understanding the strong relationship between these three concepts can vastly
improve our JavaScript programming ability, giving us a strong foundation for any
type of application development.
Functions are fundamental to JavaScript. Understanding functions in JavaScript
is the single most important weapon in your arsenal. The most important fact
about functions is that in JavaScript, functions are first-class objects. They are
treated like any other JavaScript object. Just like other JavaScript data types, they
can be referenced by variables, declared with literals, and even passed as function
parameters.
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