How to check if a string contains a number in JavaScript?

Question

I don't get how hard it is to discern a string containing a number from other strings in JavaScript.

Number('') evaluates to 0, while '' is definitely not a number for humans.

parseFloat enforces numbers, but allow them to be tailed by abitrary text.

isNaN evaluates to false for whitespace strings.

So what is the programatically function for checking if a string is a number according to a simple and sane definition what a number is?

Answer 1

By using below function we can test whether a javascript string contains a number or not. In above function inplace of t, we need to pass our javascript string as a parameter, then the function will return either true or false

function hasNumbers(t)
{
var regex = /\d/g;
return regex.test(t);
}    

Answer 2

If you want something a little more complex regarding format, you could use regex, something like this:

var pattern = /^(0|[1-9][0-9]{0,2}(?:(,[0-9]{3})*|[0-9]*))(\.[0-9]+){0,1}$/;

Demo

I created this regex while answering a different question awhile back (see here). This will check that it is a number with atleast one character, cannot start with 0 unless it is 0 (or 0.[othernumbers]). Cannot have decimal unless there are digits after the decimal, may or may not have commas.. but if it does it makes sure they are 3 digits apart, etc. Could also add a -? at the beginning if you want to allow negative numbers... something like:

/^(-)?(0|[1-9][0-9]{0,2}(?:(,[0-9]{3})*|[0-9]*))(\.[0-9]+){0,1}$/;