Read the jquery source explanation notes

1. Methods defined in Jquery.fn=jquery.prototype: init, map, each, ToArray, get, Pushstack, ready, Slice,first, Last, EQ, map,end; Properties: jquery, constructor, selector, length, push, sort, splice (the latter three are for internal use only).

2, through jQuery.fn.init.prototype = Jquery.fn; Avoid the confusion of this. This appears to JQuery.fn.init rewrite the Init method in its prototype object Jquery.fn, and then create the JQuery instance by using the new JQuery.fn.init (selector, context, rootjquery). Thus jquery also inherits all the methods and attributes in its jquery.fn.

Read the jquery source explanation notes