Clean Code in JavaScript

Immutability

This chapter has largely been about how we structure and separate our abstractions, but it is equally important to consider the expectations of the data that passes between these abstractions.

Immutability refers to the simple idea that data should not mutate. This means that, when we initialize an object, for example, we should not add new properties to it or change existing properties over time. Instead, we should derive a brand new object and only make changes to our own copy. Immutability is a characteristic of data, but is also a general tenet of functional programming. A language can also enforce immutability by disallowing the mutation of already declared variables or objects. JavaScript's const is an example of this type ...