JavaScript: Test a value, x, against a predicate function
JavaScript fundamental (ES6 Syntax): Exercise-104 with Solution
Write a JavaScript program to test a value, x, against a predicate function. If true, return fn(x). Else, return x.
Return a function expecting a single value, x, that returns the appropriate value based on pred.
- Return a function expecting a single value, x, that returns the appropriate value based on pred.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
// Define the 'when' function to conditionally apply a function to a value.
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
// Define a function 'doubleEvenNumbers' that doubles even numbers.
const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
// Test the 'doubleEvenNumbers' function with different inputs.
console.log(doubleEvenNumbers(2)); // Output: 4 (2 * 2)
console.log(doubleEvenNumbers(1)); // Output: 1 (unchanged)
Output:
4 1
Visual Presentation:
Flowchart:
Live Demo:
See the Pen javascript-basic-exercise-104-1 by w3resource (@w3resource) on CodePen.
Improve this sample solution and post your code through Disqus
Previous: Write a JavaScript program to convert a given string into an array of words.
Next: Write a JavaScript program that return true if the given value is a number, false otherwise.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.
It will be nice if you may share this link in any developer community or anywhere else, from where other developers may find this content. Thanks.
https://www.w3resource.com/javascript-exercises/fundamental/javascript-fundamental-exercise-104.php
- Weekly Trends and Language Statistics
- Weekly Trends and Language Statistics