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) {
    return typeof(id) === 'number';
}

To also check if it’s an integer:

function fn(id) {
    return typeof(id) === 'number' &&
            isFinite(id) &&
            Math.round(id) === id;
}