Discuss
  • Feature Request: Number.isNumber()

Feature Request: Number.isNumber()

# Adrian Sieber (10 years ago)

checking if a value is a number is currently really complicated and I have stumbled upon a fair amount of code where this lead to bugs.

The easiest way is typeof value === 'number'. This however has the drawback that NaN also evaluates to true. Furthermore, basically every expression preceded by a + evaluates to true. … and there are even more gotchas. For a full roundup read jonschlinkert/is-number.

This implementation could also be used as a starting point. (However, I would argue that isNumber('3') should evaluate to false. It's a string after all.)

Therefore I think a isNumber functionality should already be provided natively. What do you think?

# Álex Puchades (10 years ago)

El 10/4/2016 5:08 PM, "Adrian Sieber" <adrian.sieber1 at gmail.com> escribió:

Hi everybody,

checking if a value is a number is currently really complicated and I have stumbled upon a fair amount of code where this lead to bugs.

The easiest way is typeof value === 'number'.

What about Number.isFinite?

This however has the drawback that NaN also evaluates to true.

Number.isFinite(NaN) is false

Furthermore, basically every expression preceded by a + evaluates to

true.

… and there are even more gotchas. For a full roundup read

jonschlinkert/is-number.

This implementation could also be used as a starting point. (However, I would argue that isNumber('3') should evaluate to false. It's a string after all.)

Therefore I think a isNumber functionality should already be provided

natively.

# Adrian Sieber (10 years ago)

What about Number.isFinite?

Thanks for the heads up. I wasn't aware that there was a fixed version of isFinite added to ES2015. The global one was just a mess , but the new one seems to do exactly what I was looking for. Problem solved =). Thanks a lot!