Hands-On Design Patterns with React Native

Immutable primitives in JavaScript

In JavaScript, primitive data types (number, string, Boolean, undefined, null, and symbol) are immutable. Objects are mutable. In addition, JavaScript is loosely typed; that means the variable does not need to be of a certain type. For instance, you may declare variable A and assign the number 5 to it, and then later decide to assign an object to it. JavaScript allows that.

To simplify things, the community has created two very important movements:

• Libraries that guarantee immutability of objects
• Static type-checkers for JavaScript, such as Flow or TypeScript

The first one provides functions to create objects that guarantee their immutability. This means that, whenever you want to change something within ...