Adding an object which has a length property into a jQuery 'collection' doesn't produce the expected result. I've been unable to find documentation of this behaviour.

In code. The following happens in Firefox 9 and Chromium 14 under ubuntu.

var one = 1;
console.log( $(one), $(one).length ); // jQuery(1), 1

var arrayTwo = [2];
console.log( $(arrayTwo), $(arrayTwo).length ); // jquery([2], 1

var o = new Object;
console.log( $(o), $(o).length ); // jquery( Object {} ), 1

var EmptyFunction = function(){};
var emptyFunctionObject = new EmptyFunction();
console.log( $(emptyFunctionObject), $(emptyFunctionObject).length ); // jQuery( Object {} ), 1

// this is surprising
var Length = function( length ){ this.length = length };
var l0 = new Length(0);
var l1 = new Length(1);
var l5 = new Length(5);
console.log( $(l0), $(l0).length ); // jQuery(), 0
console.log( $(l1), $(l1).length ); // jQuery(undefined), 1
console.log( $(l5), $(l5).length ); // jQuery(undefined), undefined, undefined, undefined, undefined), 5

// same with
var oLength  = {length:2};
console.log( $(oLength), $(oLength).length ); // jQuery(undefined, undefined), 2

It seems you can't make a collection from a object with a length property. In any case the collection returned does not behave as expected.

Kind Regards, Pete