Closure

Abstract

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• Closure is a Function inside a function that remembers and has access to variables that are outside of itself, even after the outer function finishes executing. The code editor below shows a simple example

Where is inner_func when outer_func() finishes executing?

The inner_func closure is stored in the Heap Segment when it is created inside outer_func(). This also means that closure takes up Main Memory resources!!!

Since closure depends on external variables, so it isn't pure function?

Closure is Pure Function if the external variables it depends on is immutable and it maintains Referential Transparency.

Data Encapsulation with Closure

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• Data encapsulation with closure means creating private variables within a function scope that cannot be accessed directly from the outside. These private variables can only be accessed and modified through the functions defined within the same scope
• In the code example below, createBankAccount() is the function scope, balance is the private variable. deposit(), withdraw() & getBalance() are functions defined within the same scope. We are unable to access balance directly from outside of the createBankAccount as shown with console.log(myAccount.balance); at the last line of the program. We can only access it with deposit(), withdraw() & getBalance()

Better codes!

Data Encapsulation with Closure prevents exposing important data when it isn’t needed, accessing and modifying important data can only be done via a set functions which can enforce some checks!

References

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• Programming Terms: Closures - How to Use Them and Why They Are Useful - YouTube
• Closures Explained in 100 Seconds