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';
}

Or:

if (is_numeric($var)) {
    echo '$var is numeric';
}

How can I do it in jQuery/JavaScript?

Answer 1

The javascript function isNaN(variable) should do the trick. It returns true if the data is not a number.

Answer 2

See isNan

EDIT: Please look at what Christoph has suggested below. It makes sense to use isFinite as suggested.

Answer 3

function isNumber( input ) {
    return !isNaN( input );
}

isNumber({}) // false 

isNumber('13') // true

isNumber(13) // true

isNumber('test') // false

Answer 4

var x = 5;
if(typeof x == "number")
{
alert(x+" is a number!");
}

Answer 5

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

Answer 6

I'd go with

isFinite(String(foo))

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