Check that variable is a number

Question

How can I check that a variable is a number, either an integer or a string digit?

In PHP I could do:

if (is_int($var)) {
    echo \'$var is integer\'         


        

Answer 1

I'd go with

isFinite(String(foo))

See this answer for an explanation why. If you only want to accept integer values, look here.

Answer 2

function isNumeric( $probe )
{
    return parseFloat( String( $probe ) ) == $probe;
}

Answer 3

I'm pretty new to javascript but it seems like typeof(blah) lets you check if something is a number (it doesn't say true for strings). A know the OP asked for strings + numbers but I thought this might be worth documenting for other people.

eg:

function isNumeric(something){
    return typeof(something) === 'number';
}

Here are the docs

and here's a few console runs of what typeof produces:

typeof(12);
"number"
typeof(null);
"object"
typeof('12');
"string"
typeof(12.3225);
"number"  

one slight weirdness I am aware of is

typeof(NaN);
"number"

but it wouldn't be javascript without something like that right?!

Answer 4

You should use:

if(Number.isInteger(variable))
   alert("It is an integer");
else
   alert("It is not a integer");

you can find the reference in: Number.isInteger()