30-seconds-of-code/snippets/validateNumber.md

title, tags, expertise, cover, firstSeen, lastUpdated

title	tags	expertise	cover	firstSeen	lastUpdated
Validate number	math	intermediate	blog_images/flower-portrait-9.jpg	2017-12-17T17:55:51+02:00	2020-10-22T20:23:26+03:00

Checks if the given value is a number.

• Use parseFloat() to try to convert n to a number.
• Use Number.isNaN() and logical not (!) operator to check if num is a number.
• Use Number.isFinite() to check if num is finite.
• Use Number and the loose equality operator (==) to check if the coercion holds.

const validateNumber = n => {
  const num = parseFloat(n);
  return !Number.isNaN(num) && Number.isFinite(num) && Number(n) == n;
}

validateNumber('10'); // true
validateNumber('a'); // false