Mastering JavaScript

Functions, Closures, and Modules
return {
getSecret: getSecret,
getPassCode: getPassCode
};
})();
superModule.getSecret();
superModule.getPassCode();
This example satisfies both the conditions. Firstly, we create an IIFE or a named
function to act as an outer enclosure. The variables defined will remain private
because they are scoped in the function. We return the public functions to make sure
that we have a closure over the private scope. Using IIFE in the module pattern will
actually result in a singleton instance of this function. If you want to create multiple
instances, you can create named function expressions as part of the module as well.
We will keep exploring various facets of functional aspects of JavaScript and closures
in particular. There can be a lot of imaginative uses of such elegant constructs. An
effective way to understand various patterns is to study the code of popular libraries
and practice writing these patterns in your code.
Stylistic considerations
As in the previous chapter, we will conclude this discussion with certain stylistic
considerations. Again, these are generally accepted guidelines and not rules—feel
free to deviate from them if you have reason to believe otherwise:
• Use function declarations instead of function expressions:
// bad
const foo = function () {
};
// good
function foo() {
}
• Never declare a function in a non-function block (if, while, and so on). Assign
the function to a variable instead. Browsers allow you to do it, but they all
interpret it differently.
• Never name a parameter arguments. This will take precedence over the
arguments object that is given to every function scope.
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