[abaco]

FFS read the code before spouting random stuff.

(!isNaN('100') && isFinite('100'))

Negation (!) before isNaN()

[Klathmon]

he's right...

(!isNaN('100') && isFinite('100')) === true

My check would treat '100' as a number, so if i did something like this it would break unexpectedly:

    var num = '100'
    if ((!isNaN(num) && isFinite(num)) === true) {
      console.log(num + 10)
    }

You'll get "10010" printed to the console.

[abaco]

Well that's because this is checking if a value may be a valid number. It's not safely converting the value to a number. That's done after a parseFloat()

[jomamaxx]

You guys make my point for me.

There's no way on earth we'd be arguing about such a ridiculously trivial thing for most other languages.

Nobody should have to look any of this up.

Yeah, we work around it ... but it drives me crazy. :)