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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 
const composeRight = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));
const add = (x, y) => x + y;
const square = x => x * x;
const addAndSquare = composeRight(add, square);

console.log(addAndSquare(1, 2));
console.log(addAndSquare(3, 2));

Sample Output:

9
25

Pictorial Presentation:

JavaScript Fundamental: Perform left-to-right function composition

Flowchart:

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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Previous: Write a JavaScript program to perform right-to-left function composition.
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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JavaScript: Tips of the Day

Returns the difference (in days) between two dates

Example:

const tips_DiffBetweenDates = (dateInitial, dateFinal) =>
  (dateFinal - dateInitial) / (1000 * 3600 * 24);
console.log(tips_DiffBetweenDates(new Date('2020-05-13'), new Date('2020-06-05')));

Output:

23