如何检查对象是否为方法定义？

function isMethod(obj) {
  return typeof obj === 'function';
}

const obj = {
  myMethod: function() {}
};

console.log(isMethod(obj.myMethod)); // true
console.log(isMethod(obj)); // false

class MyClass {
  myMethod() {}
}

const instance = new MyClass();

console.log(instance.myMethod instanceof Function); // true

function isMethod(obj) {
  return Object.prototype.toString.call(obj) === '[object Function]';
}

const obj = {
  myMethod: function() {}
};

console.log(isMethod(obj.myMethod)); // true
console.log(isMethod(obj)); // false

function hasMethod(obj, methodName) {
  return Reflect.ownKeys(obj).includes(methodName) && typeof obj[methodName] === 'function';
}

const obj = {
  myMethod: function() {}
};

console.log(hasMethod(obj, 'myMethod')); // true
console.log(hasMethod(obj, 'nonExistentMethod')); // false