Why is it possible to query jQuery('div') like an array?

Question

I got another question regarding jQuery\'s architecture. $(\'div\') constructs a new jQuery object:

$(\'div\') instanceof jQuery; /         


        

Answer 1

Treating a jQuery object like an array is an application of duck typing. From Wikipedia:

In computer programming with object-oriented programming languages, duck typing is a style of dynamic typing in which an object's current set of methods and properties determines the valid semantics, rather than its inheritance from a particular class or implementation of a specific interface.

In other words, it's not important that the jQuery function actually return an array instance, as long as it provides the necessary properties (e.g. length, numeric indices) and methods to act like an array.

JavaScript has other array-like objects. For example, the arguments object isn't an array, either, but it has properties (like length) that allow you to pretend it is.