I already have a function for modifing other class methods:
class MyClass {
constructor() {
this.num = 1;
}
inc(){
this.num++;
}
}
runAfterMethod(classHandle, methodName, executeAfter) {
const oldHandle = classHandle.prototype[methodName];
classHandle.prototype[methodName] = function () {
const returnValue = oldHandle.apply(this, arguments);
//@ts-ignore
executeAfter.apply(this, arguments);
return returnValue;
};
}
runAfterMethod(MyClass, "inc", function() {console.log(this.num)})
new MyClass().inc(); // Prints 2
However, this does not work for the constructor of the class (because it is technically the class itself)
What I would really be happy with is something that mimics this behavior:
class MyClass {
constructor() {
this.num = 1;
}
}
extendConstructor(MyClass, function(){
this.str = "hello world"
})
new MyClass(); // num: 1, str: "hello world"
I have looked at things like How to modify the constructor of an ES6 class however, they all require = somewhere, which does not work inside of a function (where that only changes the value of the class inside the function, not the class itself)
Mutating the existing class is really weird. What would be much less of a code smell IMO would be to create a wrapper around the class that instantiates the class, then calls it with your custom callback, and then returns the instance - it'd be a lot more straightforward. Would that work for your purposes?
class MyClass {
constructor() {
this.num = 1;
}
}
const extendConstructor = (theClass, callback) => function(...args) {
const instance = new theClass(...args);
callback.call(instance);
return instance;
};
const Extended = extendConstructor(MyClass, function(){
this.str = "hello world"
})
console.log(new Extended()); // num: 1, str: "hello world"