In the jQuery, we always need determine if the a certain element existed in current object, you can use $(this).children, $(this).find(), and $(this).has(). What’s different between these 3 methods?
The .children() only travels a single level down the DOM tree, that means it’s only search son level, not grand-sons level. .find() and .has() travels down all levels to select descendant elements, but .find() can filtered by a selector, jQuery object, or element, .has() only can check a selector, but .has() will construct a new jQuery object from a subset of the matching elements.
Here is just summary of these 3 methodes, More details and examples see: