Every time the factory function is called, it generates a new class instance.
Therefore, adding the add method to the prototype of a class created by a specific call to the factory function will not affect classes produced by other calls to the same function.
The provided demonstration illustrates how you can achieve the desired outcome.
function factory() {
class A {
add(num) {
return num + 1;
}
}
return A;
}
const MyClass = factory();
MyClass.prototype.add = function (num) {
return num + 2;
};
const b = new MyClass();
console.log(b.add(1));
If the factory function is invoked again, it will yield a fresh class with an add method that only adds 1.
The subsequent example demonstrates this behavior:
function factory() {
class A {
add(num) {
return num + 1;
}
}
return A;
}
const MyClassA = factory();
const MyClassB = factory();
// Override "add" method in MyClassA
MyClassA.prototype.add = function (num) {
return num + 2;
};
console.log(new MyClassA().add(1)); // 3
console.log(new MyClassB().add(1)); // 2 (MyClassB utilizes the default "add" method)
Consequently, each invocation of the factory function necessitates the addition of the add method to the prototype.
To prevent the repeated overwriting of the add method in different calls to the factory function, one solution is to create a separate function that:
- Invokes the
factory function
- Modifies the
add method
- Returns the updated class instance
This approach allows for reusable code that updates the add method consistently.
The following code presents an example:
function factory() {
class A {
add(num) {
return num + 1;
}
}
return A;
}
function factoryWrapper() {
const MyClass = factory();
MyClass.prototype.add = function(num) {
return num + 2;
};
return MyClass;
}
const Class1 = factoryWrapper();
const Class2 = factoryWrapper();
console.log(new Class1().add(1));
console.log(new Class2().add(1));