Question

In PHP, it’s pretty easy:

is_numeric(23);//true is_numeric('23');//true is_numeric(23.5);//true is_numeric(true);//false 

But how do I do this in Javascript? I could use a regular expression, but is there a function for this?

Answer 1

What about:

function isNumber(n){     return typeof(n) != 'boolean' && !isNaN(n); } 

The isNaN built-in function is used to check if a value is not a number.

Update: Christoph is right, in JavaScript Boolean types are convertible to Number, returning the 1 for true and 0 for false, so if you evaluate 1 + true the result will be 2.

Considering this behavior I’ve updated the function to prevent converting boolean values to its numeric representation.