How to Check Decimal Numbers in JavaScript with IsNumber()

Other Questions JavaScript
1

How can I effectively check if a value is a decimal number in JavaScript?

It would be great if the solution is straightforward and easy to understand, with an emphasis on cross-platform compatibility.

Here are some test cases I would like to see covered:

01. IsNumber('-1')      => true
02. IsNumber('-1.5')    => true
03. IsNumber('0')       => true
04. IsNumber('0.42')    => true
05. IsNumber('.42')     => true
06. IsNumber('99,999')  => false
07. IsNumber('0x89f')   => false
08. IsNumber('#abcdef') => false
09. IsNumber('1.2.3')   => false
10. IsNumber('')        => false
11. IsNumber('blah')    => false
2

You can use the parseFloat() function combined with a regex check for decimals. parseFloat('-1.5') gives -1.5, a number. Using /^[-+]?[0-9]*\.?[0-9]+$/ regex before parseFloat ensure only valid decimal numbers. Remember, isNaN is your friend to check final results after these steps! :smiling_face: