what is functional javascript in javascript

Functional JavaScript refers to the practice of using functional programming concepts and techniques in JavaScript code. Functional programming is a programming paradigm that emphasizes writing code in a declarative and composable manner by treating functions as first-class citizens.

To write functional JavaScript code, you can follow the following principles and techniques:

1. Pure Functions: A pure function is a function that always returns the same output for the same input and does not have any side effects. It does not modify any external state or variables. Pure functions are predictable and easier to test and reason about.

Example of a pure function:

index.tsx
function add(a, b) {
  return a + b;
}
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2. Immutability: Functional programming promotes immutability, which means avoiding changing the state of objects or variables once they are created. Instead of modifying an object, you create a new object with the desired changes.

Example of immutability in JavaScript:

index.tsx
const array = [1, 2, 3];
const newArray = [...array, 4]; // creates a new array with an additional element
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3. Higher-Order Functions: Higher-order functions are functions that can take other functions as arguments or return functions as results. Higher-order functions enable you to write more reusable and composable code.

Example of a higher-order function:

index.tsx
function multiplyBy(factor) {
  return function (num) {
    return num * factor;
  };
}

const multiplyByTwo = multiplyBy(2);
console.log(multiplyByTwo(4)); // Output: 8
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4. Function Composition: Function composition is the act of combining two or more functions to create a new function. It allows you to build complex behavior by chaining small, focused functions together.

Example of function composition:

index.tsx
function addOne(num) {
  return num + 1;
}

function multiplyByTwo(num) {
  return num * 2;
}

const addOneAndMultiplyByTwo = compose(multiplyByTwo, addOne);
console.log(addOneAndMultiplyByTwo(5)); // Output: 12
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These are just some of the core concepts of functional programming in JavaScript. By applying these principles, you can write cleaner, more maintainable, and testable code.