How do I check if a JavaScript parameter is a number?

Question

I\'m doing some trouble-shooting and want to add a check that a parameter to a function is a number. How do I do this?

Something like this...

function fn         


        

Answer 1

function fn(id) {
    var x = /^(\+|-)?\d+$/;
    if (x.test(id)) {
        //integer
        return true;
    }
    else {
        //not an integer
        return false;
    }
}

Test fiddle: http://jsfiddle.net/xLYW7/