Modify Class Method Definition in TS or JS

I have a class having structure like :

class A {
    constructor() {}
    myMethod() {
      console.log('in my method');
    }
}

I want to make a method that will accept className and methodName like :

modifyClassMethod(className, methodName)

This method should wrap the whole body of methodName specified into a callback during runtime.

So if I do,

modifyClassMethod(A, myMethod)

Now during runtime the body of myMethod of class A should get changed to

myMethod() {
   nr.recordMe('here', {
      console.log('in my method').
   })
} 

Now when I will create a new object of A class, then I will get modified value of myMethod.

How can I achieve this in TS or JS ?.