The extend of jquery source code

Jquery.extend = JQuery.fn.extend = function () {

Define some variables

if () {} See if it is a deep copy case

if () {} See the parameter is correct

if () {} see if plug-in situation

for () {There may be multiple object conditions

if () {} Prevents circular references, such as $.extend (A, {name:a}); The case of circular references is excluded;

if () {} deep copy

else if () {} shallow copy

}

}

Knowledge Point carding:

1, jquery is a function, jquery () returns an object, the constructor of this object is JQuery.fn.init (), the constructor of the prototype, that is, JQuery.fn.init.prototype = Jquery.fn, and Jquery.fn = Jquery.prototype, so the prototype function of the paparazzi function jQuery.fn.init () is Jquery.prototype, Summary: The object returned after calling JQuery () is actually inherited from Jquery.prototype prototype;

2, jquery Use the same set of source code for the expansion of static and instance methods, jquery uses two kinds of extend form analysis:

Jquery.extend (): Expanding static methods

JQuery.fn.extend (): extended instance method

$.extend (), this points to $, which is the jquery function, add method Aaa:this.aaa, $.AAA ()

$.fn.extend (), this points to $.fn = Jquery.prototype, adding the method Aaa:this.aaa-$ () in the prototype. AAA (), you need to call the AAA method in the instance object

"When writing only one object argument, JQ expands the two forms of the plugin"

$.extend ({//Extension tool method

Aaa:function () {alert (1);},

Bbb:function () {alert (2);}

});

$.AAA (); Pop up 1

$.BBB (); Pop Up 2

$.fn.extend ({//Extended JQ instance method

Aaa:function () {alert (3);},

Bbb:function () {alert (4);}

});

$ (). AAA ();

$ (). BBB ();

"When writing to an object argument, the following objects are extended to the first object"

var a = {}; Extending the properties of object a

$.extend (A, {name: "Hello"}, {age:30});

alert (a); Popup {name: "Hello", age:30}

var a = {}; You can also make deep and shallow copies.

var b = {name: {age:30}};

$.extend (A, b); $.extend () make a shallow copy!

A.name.age = 20;

alert (b.name.age); Pop up 20

$.extend (True, A, b); Add parameter True to tell JQ I want to make a deep copy

A.name.age = 20;

alert (b.name.age); Pop up 30

3. About inheritance

JQ uses copy inheritance, more flexible;

Class inheritance: Using the new constructor for inheritance;

Prototype inheritance:??

The extend of jquery source code