这些方法之间有任何技术差异吗？ [重复]
[英]Is there any technical difference between these methods? [duplicate]
This question already has an answer here:
这个问题在这里已有答案：
- Use of 'prototype' vs. 'this' in JavaScript? 14 answers
- 在JavaScript中使用'prototype'与'this'？ 14个答案
I have been trying to learn OO JS. I was playing with different patterns, wrote following example.
我一直在努力学习OO JS。我正在玩不同的模式，下面的例子写道。
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?
这里的功能a和b有什么区别吗？
2 个解决方案
#1
1
this.a will be a separate function for every object you create:
this.a将是您创建的每个对象的单独函数：
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.
这意味着this.a = function（）{...}将为每个实例消耗内存，这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.
在您的代码中，a是实例的函数，而b是类的函数。
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.
就他们实际工作而言，他们之间并没有太大的不同。但是，假设你把var test = 123;在obj函数内部。 a将能够访问它，但b不会。
Additionally, you can overwrite instance.a with another function, and it will only affect the current instance.
此外，您可以使用其他函数覆盖instance.a，它只会影响当前实例。
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是对象的每个实例的单独的函数对象。如果您有大量实例，这可能会成为内存使用方面的问题。
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