原型中原始類型的行爲

Question

每個實例都有一個到創建它的構造函數原型的鏈接。所以每個實例都共享原型成員。如果通過一個實例對共享原型成員進行更改，則會反映到所有其他實例。爲什麼這似乎不符合基本類型工作，因爲可以看到下面：

//creating an empty object type 
function OBJTYPE(){}; 

//adding primitive value and reference value as a memeber to 
//the prototype of the object type 
OBJTYPE.prototype.value = 0; 
OBJTYPE.prototype.arr = ["red","green","blue"]; 

//creating instances of the object type 
var obj1 = new OBJTYPE(); 
var obj2 = new OBJTYPE(); 

//outputting the prototype members through both the instances  
document.write(obj1.value + "<br />"); //0 
document.write(obj2.value + "<br />"); //0 
document.write(obj1.arr + "<br />"); //red,green,blue 
document.write(obj2.arr + "<br />"); //red,green,blue 

//changing value of primitive member 
obj1.value = 1; //creates a new instance property 

//modifying the reference type member - pushing a value on the array 
obj1.arr.push("black"); //modifies the prototype property 

//outputting the prototype members through both the instances  
document.write(obj1.value + "<br />"); //1 //.value from instance 
document.write(obj1.__proto__.value + "<br />"); //0 //.value from prototype 
               //works in Firefox, Safari, and Chrome 
document.write(obj2.value + "<br />"); //0 //.value from prototype 

document.write(obj1.arr + "<br />"); //red,green,blue,black 
document.write(obj2.arr + "<br />"); //red,green,blue,black 

正如你可以在上面看到改變原始成員的價值創造，而不是覆蓋同名屬性調用value上obj1一個新的實例屬性，在原型中。因此，當訪問obj1.value屬性時，它會返回屏蔽原型屬性的實例屬性。這就是爲什麼兩個實例顯示不同值value。

但是，這不引用類型的行爲不像從上面可以看出。爲什麼？

Answer 1

您正在推送到ar不像你用原始值那樣分配一個新的數組。這將如預期：

obj1.value = 1; 
obj1.arr = []; 

需要注意的是從來沒有設置一個值上設置的雛形，但對象本身。

Answer 2

當您寫入對象的屬性時，新值將存儲在對象上，而不是原型。

數組的問題你必須是這樣的：

1. 給我上存儲OBJ1數組，並修改該數組： obj1.arr.push（「黑」）;

2. 撰寫OBJ1的實例的新值： obj1.arr = [1,2,3];

我會擴大，如果你需要我。

---

是的，有很多方法可以做到這一點，這取決於你需要什麼。

1對我來說最明顯的是你想要相同的對象，在這種情況下，我只是做一個對象。

var obj1 = { 
"arr": [], 
"value": 0 
}; 
// I can garuntee any editing you do on obj1 will be reflected on obj2 
var obj2 = obj1; 

2製作原型存取方法：

function OBJTYPE(){}; 

//adding primitive value and reference value as a memeber to 
//the prototype of the object type 
OBJTYPE.prototype.value = 0; 
OBJTYPE.prototype.arr = ["red","green","blue"]; 
OBJTYPE.prototype.proto = function (name, optValue) { 
if (arguments.length === 2) { 
    return OBJTYPE.prototype[name] = optValue; 
} 

return OBJTYPE.prototype.proto[name]; 
}; 

var obj1 = new OBJTYPE(); 
var obj2 = new OBJTYPE(); 

obj1.proto('value', 1); //on the prototype 
// The rest will behave like desired 

3商店直接鏈接到原：

function OBJTYPE(){}; 

//adding primitive value and reference value as a memeber to 
//the prototype of the object type 
OBJTYPE.prototype.value = 0; 
OBJTYPE.prototype.arr = ["red","green","blue"]; 
OBJTYPE.prototype.proto = OBJTYPE.prototype; 
//creating instances of the object type 
var obj1 = new OBJTYPE(); 
var obj2 = new OBJTYPE(); 

//changing value of primitive member 
obj1.proto.value = 1; //on the prototype 
// The rest will behave like desired 

4最後但並非最不重要的，使用ES5的方法getPrototypeOf

function OBJTYPE(){}; 

OBJTYPE.prototype.value = 0; 
OBJTYPE.prototype.arr = ["red","green","blue"]; 
//creating instances of the object type 
var obj1 = new OBJTYPE(); 
var obj2 = new OBJTYPE(); 

//changing value of primitive member 
Object.getPrototypeOf(obj1).value = 1; //on the prototype 
// The rest will behave like desired