404

Is there is any function like isNumeric in pure JavaScript?

I know jQuery has this function to check the integers.

Improve this question
3

6 Answers 6

Reset to default
682

There's no isNumeric() type of function, but you could add your own:

function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

NOTE: Since parseInt() is not a proper way to check for numeric it should NOT be used.

Improve this answer
Sign up to request clarification or add additional context in comments.

18 Comments

This solution is used in / taken from Jquery library $.isNumeric(obj) api.jquery.com/jquery.isnumeric
@Matt My comment was aimed at the comment and the note in the answer stating parseInt was the wrong way of doing this (then going ahead and using parseFloat, which doesn't really seem different). Interestingly isFinite will get you the result you're after in almost all cases on its own (apart from whitespace strings, which for some reason return true), so parseInt vs parseFloat seems irrelevant in this context. I certainly can't find a single input to that function where parseInt makes a difference.
DON'T USE THIS FUNCTION it does not work with floats. See jQuery's isNumeric here for ideas on implementing it.
What about Number.isInteger()? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
Careful. This function returns true for single element arrays containing a numeric element: isNumeric([0]) === true and isNumeric(['123']) === true
|
211

This should help:

function isNumber(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

Very good link: Validate decimal numbers in JavaScript - IsNumeric()

Improve this answer

Comments

109 
function IsNumeric(val) {
    return Number(parseFloat(val)) == val;
}
Improve this answer

10 Comments

I think the updated version of this is actually the best answer here. I find it odd that it has the least up-votes. I thought at first that it might fail if IsNumeric was called with NaN, but due to the quirk of NaN that it's not equal to anything it actually works out fine.
And I think you can also drop the cast to Number() and rely on the double equals to do a bit of conversion: let isNumeric = (val) => parseFloat(val) == val;
As per my requirement which I believe many other developers would have it should be function IsNumeric(val) { return Number(val)==val; } So that it ignores in case of empty string. Because I only want to validate if there is invalid value entered. While allowing empty string which is not number. I think all three answers are good based on scenarios
Explain the code please. Why not Number(val).toString() == val.toString()?
if Val is undefined then .ToString will throw exception
|
21

There is Javascript function isNaN which will do that.

isNaN(90)
=>false

so you can check numeric by 

!isNaN(90)
=>true
Improve this answer

5 Comments

except for "" and true and false which are not-not-a-number ...
I get isNaN(null) === false
isNaN("null") === true; isNaN(null) === false; for me too
isNaN(true) === false; isNaN(false) === false;
console.log(isNaN('34.234,23')); // true :-(
19 
var str = 'test343',
    isNumeric = /^[-+]?(\d+|\d+\.\d*|\d*\.\d+)$/;

isNumeric.test(str);
Improve this answer

5 Comments

Well, depending on the use case, it might actually be the worst answer here. For example, this returns false against ' 1' or '0x01', localization is not taken into account...
I kinda like this answer better, if you are reading chunks from a string or an user input, isNaN and parseInt can result in unwanted false positives like "123abc", "2e1", "0x2", etc.. (even jQuery.isNumeric will parse true). I would use something like this function isNumeric(str) { return /^\d*\.{0,1}\d*$/.test(str); }
Well, depending on the use case, it might actually be the best answer here.
As long as you trim strings and aren't worried about alternative representations this is a reasonable answer.
You didn't cater for Locale. Thousands and Decimal separators can be other way around in some countries.
12

isFinite(String(n)) returns true for n=0 or '0', '1.1' or 1.1,

but false for '1 dog' or '1,2,3,4', +- Infinity and any NaN values.

Improve this answer

2 Comments

isFinite(null) --> true, isFinite([]) --> true, isFinite('') true
As of ES2015 there is Number.isFinite

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.