Question 287977 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Regex vs IsNaN: which is better to use for checking an input is a number performance wise

To check whether a given input is a number, which of the following approaches are more efficient?

!isNaN(input)

OR using regex,

var regex=/^[0-9]+$/;
(x.match(regex))

P.S I’m ignoring empty string ("") for now which will return true for !isNaN("")

Tags:

2

Answers


  1. 0

    if you SIMPLY want to check whether a given input is a number
    then i think using ‘isNan()’ would suffice
    it works for both integer numbers as well as decimals.
    // emphasis on ‘SIMPLY’

    Login or Signup to reply.
  2. 0

    There’s a little impact on performance in both cases unless you want to parse a million strings or so. However here is a little benchmark parsing 1 mio. strings per solution. Could be improved of course. In my case (Chromium on KUbuntu) !isNaN() is faster.

    let t = performance.now();
for (let i = 0; i < 1000000; i++)
{
  let input = String(i);
  let output = !isNaN(input);
}
console.log("!isNaN() took " + (performance.now() - t));

t = performance.now();
let regex=/^[0-9]+$/;
for (let i = 0; i < 1000000; i++)
{
  let input = String(i);
  let output = input.match(regex);
}
console.log("match() took " + (performance.now() - t));
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search