Skip to content

README.md

Latest commit

 

History

History
78 lines (55 loc) · 3.34 KB

README.md

File metadata and controls

78 lines (55 loc) · 3.34 KB

JavaScript Functional Programming

Functional programming (FP) is a programming paradigm where programs are constructed by applying and composing functions.

Key Concepts of Functional Programming

  • First-Class Functions: Functions are treated as first-class citizens, meaning they can be assigned to variables, passed as arguments, and returned from other functions.
  • Pure Functions: A pure function is a function that, given the same inputs, always returns the same output and does not cause any side effects (e.g., modifying external state).
  • Immutability: Data should not be changed once created. Instead, new data structures should be created by copying and modifying the original data.
  • Higher-Order Functions: Functions that can take other functions as arguments or return them as results.
  • Function Composition: The process of combining two or more functions to produce a new function.
  • Declarative Code: Writing code that describes what you want to achieve, rather than how to achieve it. This often leads to more readable and concise code.

1. First-Class Functions

Functions can be assigned to variables, passed as arguments, and returned from other functions.

const add = (a, b) => a + b;
const result = add(2, 3);
console.log(result); // 5

2. Pure Functions

A pure function returns the same output for the same input and has no side effects.

const square = (x) => x * x;
console.log(square(4)); // 16

3. Immutability

Creating new data structures rather than modifying existing ones.

const numbers = [1, 2, 3, 4];
const incrementedNumbers = numbers.map((num) => num + 1);
console.log(numbers); // [1, 2, 3, 4]
console.log(incrementedNumbers); // [2, 3, 4, 5]

4. Higher-Order Functions

Functions that take other functions as arguments or return functions as results.

const greet = () => "Hello";
const executeFunction = (fn) => fn();
console.log(executeFunction(greet)); // "Hello"

5. Function Composition

Combining functions to create new functions.

const multiplyBy2 = (x) => x * 2;
const subtract3 = (x) => x - 3;
const multiplyAndSubtract = (x) => subtract3(multiplyBy2(x));
console.log(multiplyAndSubtract(5)); // 7

Common Functional Programming Methods in JavaScript 📦

  • map(): Creates a new array by applying a function to each element of the original array.
  • filter(): Creates a new array with elements that pass a test provided by a function.
  • reduce(): Applies a function against an accumulator and each element of the array to reduce it to a single value.
  • forEach(): Executes a function for each element in the array.

Benefits of Functional Programming

  1. Predictability: Pure functions with no side effects are easier to understand and test.
  2. Maintainability: Immutability and declarative code lead to more maintainable codebases.
  3. Reusability: Functions are reusable and can be composed in various ways to create new functionality.

Further Reference: First-class Function, JavaScript Higher Order Functions & Arrays, What are Pure Functions? | Javascript Functions Tutorial