30. What is the implementation principle of jQuery's attribute copy, and how to achieve shallow copy?

The jQuery.extend() function is used to merge the contents of one or more objects into the target object.

grammar

$.extend( target [, object1 ] [, objectN ] )

Indicates whether the merge is deep

$.extend( [deep ], target, object1 [, objectN ] )

Note: Passing false for the first parameter is not supported.

Deep copy: The deep copy code sets the first argument of the extend function to true: (recursive copy of the object referenced by the original object property) var newObject = $.extend(true, {},oldObject);

Shallow copy: the first argument is not passed in the extend function of the shallow copy code, the default is false (only copy of the original object reference) var newObject = $.extend({}, oldObject);