JavaScript: Perform left-to-right function composition

JavaScript fundamental (ES6 Syntax): Exercise-67 with Solution

Write a JavaScript program to perform left-to-right function composition.

  • Use Array.prototype.reduce() to perform left-to-right function composition.
  • The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define a function 'composeRight' that takes any number of functions as arguments and returns a new function.
const composeRight = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));

// Define functions 'add' and 'square'.
const add = (x, y) => x + y;
const square = x => x * x;

// Create a new function 'addAndSquare' by composing 'add' and 'square' in the right-to-left order.
const addAndSquare = composeRight(add, square);

// Example usage:
console.log(addAndSquare(1, 2)); // Output 9  
console.log(addAndSquare(3, 2)); // Output 25  



Visual Presentation:

JavaScript Fundamental: Perform left-to-right function composition


flowchart: Perform left-to-right function composition

Live Demo:

See the Pen javascript-basic-exercise-67-1 by w3resource (@w3resource) on CodePen.

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Next: Write a JavaScript program that accepts a converging function and a list of branching functions and returns a function that applies each branching function to the arguments and the results of the branching functions are passed as arguments to the converging function.

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