Identifying if a function is within the prototype chain of a class instance in ES6

Question

Identifying if a function is within the prototype chain of a class instance in ES6

Consider the following ES6 class:

class C {
  x () { }
  fnIsMethodOfC (fn) { return /* ? */ }
}

Along with various functions like

function y () {}
z = () => {}

What is an efficient way to determine if a function is a method of C, for example:

c = new C()
c.fnIsMethodOfC(c.x) === true
c.fnIsMethodOfC(C.prototype.x) === true
c.fnIsMethodOfC(y) === false
c.fnIsMethodOfC(z) === false

While one could potentially recursively search through the prototype chain, it may not be the most optimal solution.

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Answer 1

Answer №1

Perhaps a potential solution could be:

function checkIfMethodBelongsToClass(method, className) {
  const prototype = Object.getPrototypeOf(className)
  return prototype && prototype[method.name] === method
}

Answer 2

Perhaps a potential solution could be:

function checkIfMethodBelongsToClass(method, className) {
  const prototype = Object.getPrototypeOf(className)
  return prototype && prototype[method.name] === method
}

Answer 3

Answer №2

function checkMethod(fn) {
  if(!fn || !fn.name) return false;
  return !!this[fn.name] && fn !== this[fn.name];
}

In addition to that, this function will also perform an additional check to see if the actual function is different.

Answer 4

function checkMethod(fn) {
  if(!fn || !fn.name) return false;
  return !!this[fn.name] && fn !== this[fn.name];
}

In addition to that, this function will also perform an additional check to see if the actual function is different.

Identifying if a function is within the prototype chain of a class instance in ES6

Answer №1

Answer №2

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