1.Class的內部所有定義的方法，都是不可列舉的。

const funName = 'fun';
//類Demo		
class Demo{
	constructor(arg) {
	    
	}
	say(){
		
	}
	speak(){
		
	}
	[funName](){
		
	}
}

console.log( Object.keys(Demo.prototype) )	//[]
console.log(Object.getOwnPropertyNames(Demo.prototype))//["constructor", "say", "speak", "fun"]


//建構函式F
 

function F(){}
F.prototype.say = function(){};
F.prototype.speak = function(){}
F.prototype[funName] = function(){}

console.log( Object.keys(F.prototype) )	//["say", "speak", "fun"]
console.log( Object.getOwnPropertyNames(Demo.prototype) )//["constructor", "say", "speak", "fun"]

其中，參考【Javascript屬性列舉的5個方法比較

2.檢測物件的屬性是否可列舉：

const isEnumerable = (prop, obj) => 
(Object.getOwnPropertyNames(obj).indexOf(prop)) > -1 && (Object.keys(obj)
 
.indexOf(prop) > -1);

isEnumerable是Boolean型別，返回true表示屬性可列舉，false為不可列舉

isEnumerable('say', Demo.prototype) 		//false
isEnumerable('speak', Demo.prototype) 		//false
isEnumerable('constructor', Demo.prototype) 		//false

isEnumerable('say', F.prototype) 		//true
isEnumerable('speak', F.prototype) 		//true
isEnumerable('constructor', F.prototype) 		//false