Question

I started to learn Jquery and but I am having trouble understanding function parameters:(
If you look my first code and run it: my script WILL work (WITHOUT parameters). And if you look my second code
(WITH parameters) and run it: second script WILL ALSO WORK!!

My first question: Did I correctly set parameter in my second script?
Second question: How can I check is my parameter set or being passed correctly to my function?

P.S. Sorry for being NOOB and THANK YOU!!

   //First code (WITHOUT PARAMETERS!!!) 
   $(document).ready(function () {
       var addclass = $('p:first');

       function AddClass() {
           addclass.addClass('first');
           if (addclass.is($('.first'))) {
               alert('here');
           }
           else {
               alert('not here');
           }
       }
       $('.button').click(function () {
           AddClass(addclass);
       });
   });
   //Second code (WITH PARAMETERS)
   $(document).ready(function () {
       var addclass = $('p:first');

       function AddClass(addclass) {
           addclass.addClass('first');
           if (addclass.is($('.first'))) {
               alert('here');
           }
           else {
               alert('not here');
           }
       }
       $('.button').click(function () {
           AddClass(addclass);
       });
   });

Answer 1

your second arguments is right and to check any arguments passed to a function use:

arguments.length

for example:

function myfunc() {
   alert( arguments.length ); //output: 1, because you passed one argument

   // and to get that

   var myarg = arguments[0];
}

myfunc(someVar);

If you don’t pass any arguments then:

function myfunc() {
   alert( arguments.length ); //output: 0, because you passed no argument
}

myfunc();

For your function:

  function AddClass(addclass) {

                      ^-- declaring addclass is not necessary if you use like following

       // checking for argument

       if( arguments.length ) {
         // arguments[0] will give you addclass
         // you may not write addclass to function like above
       }

       addclass.addClass('first');
       if (addclass.is($('.first'))) {
           alert('here');
       }
       else {
           alert('not here');
       }
   }

Call function with addclass arguments:

   $('.button').click(function () {
       AddClass(addclass);
   });