這些方法之間有任何技術差異嗎？ [重復]
[英]Is there any technical difference between these methods? [duplicate]
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- Use of 'prototype' vs. 'this' in JavaScript? 14 answers
- 在JavaScript中使用'prototype'與'this'？ 14個答案
I have been trying to learn OO JS. I was playing with different patterns, wrote following example.
我一直在努力學習OO JS。我正在玩不同的模式，下面的例子寫道。
var obj = function() {
this.a= function() {
return 'a';
}
}
obj.prototype.b = function() {
return 'b';
}
var instance = new obj();
console.log(instance.a());
console.log(instance.b());
Is there any difference here in function a and b?
這里的功能a和b有什么區別嗎？
2 个解决方案
#1
1
this.a will be a separate function for every object you create:
this.a將是您創建的每個對象的單獨函數：
var obj = function() {
this.a= function() {
return 'a';
}
}
obj.prototype.b = function() {
return 'b';
}
var instance1 = new obj();
var instance2 = new obj();
console.log(instance1 === instance2); // false: different instances
console.log(instance1.a === instance2.a); // false: different functions (this.a)
console.log(instance1.b === instance2.b); // true: obj.prototype.b
This means that this.a = function(){ ... } will consume memory for every instance, something you most likely want to avoid.
這意味着this.a = function（）{...}將為每個實例消耗內存，這是您最可能想要避免的。
#2
1
In your code, a is a function of the instance, whereas b is a function of the class.
在您的代碼中，a是實例的函數，而b是類的函數。
In terms of them actually working, there isn't much different between them by themselves. However, let's say you put var test = 123; inside the obj function. a will be able to access it, but b will not.
就他們實際工作而言，他們之間並沒有太大的不同。但是，假設你把var test = 123;在obj函數內部。 a將能夠訪問它，但b不會。
Additionally, you can overwrite instance.a with another function, and it will only affect the current instance.
此外，您可以使用其他函數覆蓋instance.a，它只會影響當前實例。
On the other hand, a is a separate function object for each instance of the object. This could become a problem in terms of memory use if you have large numbers of instances.
另一方面，a是對象的每個實例的單獨的函數對象。如果您有大量實例，這可能會成為內存使用方面的問題。
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