Functional programming (FP) emphasizes immutability, pure functions, and declarative constructs. Here are key patterns and principles to master:

1. Pure Functions

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

  • ✅ Advantages: Easier to test, debug, and reason about.
  • 📌 Example: 
    const add = (a, b) => a + b;
    Pure_Function

2. Immutability

Avoid modifying data directly. Use transformations to create new states.

  • 🔄 Pattern: Use .map() or .filter() instead of for-loops.
  • 📌 Example: 
    new_list = [x * 2 for x in original_list]
    Immutability

3. Higher-Order Functions

Functions that take other functions as arguments or return them.

  • 🧠 Use Cases: Data processing pipelines, event handling.
  • 📌 Example: 
    [1,2,3].map { |x| x**2 }.reduce(:+)
    Higher_Order_Function

4. Recursion

Replace loops with recursive functions for elegant solutions.

  • 📌 Example: 
    factorial 0 = 1  
factorial n = n * factorial (n-1)
    Recursion

5. Avoid Side Effects

Keep functions focused on their core logic.

  • 🚫 Bad Practice: 
    let counter = 0;  
function increment() { counter++; }
  • ✅ Better Practice: 
    const increment = (count) => count + 1;

For deeper insights, check our Functional Programming Tutorial.

Functional_Programming