Immutability

A higher order function is any function that takes a function as an argument, returns a function, or both. Higher order functions are often used to:

• Abstract or isolate actions, effects, or async flow control using callback functions, promises, monads, etc…
• Cre...

A pure function is a function which:

• Given the same inputs, always returns the same output, and
• Has no side-effects

Pure functions have lots of properties that are important in functional programming.

Function composition is the proces...

Shared state is any variable, object, or memory space that exists in a shared scope, or as the property of an object being passed between scopes. 

A shared scope can include global scope or closure scopes. Often, in object oriented programming, objects are shared betwe...

Functional programming (often abbreviated FP) is the process of building software by composing pure functions, avoiding shared state, mutable data, and side effects. Functional programming is declarative rather than imperative, and application state flows through...

A side effect is any application state change that is observable outside the called function other than its return value. Side effects include:

• Modifying any external variable or object property (e.g., a global variable, or a variable in the parent function scope chain...