How to test if a parameter is provided to a function?

Question

I was wondering, can you create a function with an optional parameter.

Example:

function parameterTest(test)
{
   if exists(test)
   {
     alert(\'t         


        

Answer 1

function parameterTest(p) {
    if ( p === undefined)
        alert('The parameter doesn\'t exist...');
    else
        alert('the parameter exists...');
}