jQuery.each() undefined issue

Question

I have the following code

function myFunction(items) {
   // this prints out 11
   alert(items.length);

   $(items).each(function(i, item) {
       // item is undefined for some reason
   }
}

It I alert the length of items, it has elements in it (11 to be exact). so how could 11 items be present, but jQuery still pass undefined?

Answer 1

The only explanation for this is the that items array contains values which are undefined, i.e :

items = [undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined];

Both of the other answers are wholly incorrect. The first parameter of each is the index, not the value, and jQuery.fn.each calls jQuery.each. There is no disambiguation between them.

Answer 2

It sounds like you are not passing a jQuery wrappet set to your function. If you pass an array or an object you need to use the jQuery helper function $.each() like

$.each(items, function(index, element){
});

As I already mentioned several times in other answers, it is bad practice to loop over an array with .each() or javascripts native for..in.

If you are passing arrays use a standard for loop.

edit

As it turns out, you actually really can call the jQuery constructor with a standard array. But it seems like terrible karma to do so, you can't call 95% of all those jQuery methods, unless you want to crash / corrupt your code.