本文主要講解js中幾種實現繼承的方法。
通過【某種方式】讓乙個物件可以訪問到另乙個物件中的屬性和方法，我們把這種方式稱之為繼承 並不是所謂的*** extends yyy。
這裡構造乙個父建構函式animal()：
function
animal
(age, name)
}//原型方法
animal.prototype.
sleep
=function()
//原型屬性
animal.prototype.type =
"animal"
;
子建構函式.prototype = 父建構函式.prototype，思考一下，這樣的做法的特點：
function
dog(
)dog.prototype = animal.prototype;
//自定義原型物件時，盡量重寫constructor再指向該函式
dog.prototype.constructor = dog;
var dog1 =
newdog()
;dog1.
say();
is not a function
dog1.
sleep()
;//undefined is sleeping
var dog2 =
newdog()
;dog2.__proto__.type =
"dog"
;console.
log(dog1.type)
;//dog
子建構函式.prototype = new 父建構函式()，思考一下該繼承的特點：
function
dog(name)
dog.prototype =
newanimal(6
,"animal");
var dog1 =
newdog
("dog1");
var dog2 =
newdog
("dog2");
console.
log(dog1.age)
;//6
dog1.
say();
//i am dog1, and 6 years old
console.
log(dog1.type)
;//animal
dog1.
sleep()
;//dog1 is sleeping
dog2.friend.
push
("dog1");
console.
log(dog1.friend)
;//["dog1"]
function
dog(arg)
var dog1 =
newdog([
6,"dog1"])
;var dog2 =
newdog([
7,"dog2"])
;dog1.
say();
//i am dog1, and 6 years old
dog2.
say();
//i am dog2, and 7 years old
dog1.
sleep()
; uncaught typeerror: dog1.sleep is not a function
建構函式繼承 + 原型鏈繼承，思考這種繼承方式的特點：
function
dog(arg)
dog.prototype =
newanimal()
;var dog1 =
newdog([
6,"dog1"])
;var dog2 =
newdog([
7,"dog2"])
;dog1.
say();
//i am dog1, and 6 years old
dog2.
say();
//i am dog2, and 7 years old
dog1.
sleep()
;//dog1 is sleeping
dog2.
sleep()
;//dog2 is sleeping
dog1.__proto__.type =
"dog1"
;console.
log(dog2.__proto__.type)
;//dog1
建構函式繼承 + 僅僅繼承父原型例項的原型鏈繼承，它兼有組合繼承的優點，同時修復了它的缺點，特點如下：
function
dog(arg)
dog.prototype = object.
create
(animal.prototype)
;dog.prototype.constructor = dog;
var dog1 =
newdog([
6,"dog1"])
;var dog2 =
newdog([
7,"dog2"])
;dog1.
say();
//i am dog1, and 6 years old
dog2.
say();
//i am dog2, and 7 years old
dog1.
sleep()
;//dog1 is sleeping
dog2.
sleep()
;//dog2 is sleeping
dog1.__proto__.type =
"dog1"
;console.
log(dog2.__proto__.type)
;//dog1
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