We know that using prototype chains to implement inheritance is a goodway:) See an example of prototype chain inheritance.
function A () {
= 44;
}
= function (){
return ;
};
function B() {
}
= new A(); // B completes inheritance through the instance of A and forms a prototype chain (B's prototype is the instance of A)var b = new B();
();
The relationship is as follows: b (instance) -> = new A() -> ->
However, there are indeed problems in this seemingly "beautiful" inheritance method.
1. The main problem comes from the prototype containing reference type values. We know that there is a problem with the shared prototype, throw an example
function Person () {
}
= {
friends = ["a","b"];
}
var person1 = new Person();
var person2 = new Person();
("c");
(); // "a","b","c"
(); //"a","b","c"
The original value in the prototype is changed by referencing the instance, and it also affects other instances. (That's why reference type values are defined in the constructor rather than in the prototype)
The same situation will occur in the prototype chain:
function A () {
= [1,2,3];
}
function B() {
}
= new A();
var b = new B();
var a = new A();
(4);
; //1234
var b2 = new B();
; //1234
; //123
We see the same situation as above (when inheriting through the prototype, the prototype will actually become another type of instance. So the original instance attribute naturally becomes the current prototype attribute).
But we see the instance of A; it is still 123, which means that when B inherits the instance of A, all attributes in the instance of A (including the prototype pointer, forming the prototype chain) are not referenced (in fact, there is a question here, is it because it inherits the instance of A() so it will not affect the performance of A() creating other instances?).
2. When creating subclass instances, you cannot pass parameters to the superclass without affecting all object instances.
function A (light) {
this.light1 = light;
};
function B (light) {
= light;
};
//While assigning a value to B, you can't achieve it if you want to assign a value to A, but you can't = new A();
var C = new B(123);
();
(C.light1);
To implement this, you need to call A's constructor manually, which will affect other instances
function A (light) {
this.light1 = light;
};
function B (light) {
= light;
(this,light);//Manually call A's constructor};
//Assign value to B, assign value to A while = new A();
var C = new B(123);
();
(C.light1);
The above is an analysis of the problems existing in JavaScript in JavaScript introduced by the editor. I hope it will be helpful to everyone. If you have any questions, please leave me a message and the editor will reply to everyone in time. Thank you very much for your support for my website!