'use strict';
let Janken = function(handarr = ['グー','チョキ','パー']){
this.handarr = handarr;
}
Janken.prototype.getNPCHand = function(){
let arrnum = Math.floor(Math.random() * this.handarr.length);
return this.handarr[arrnum];
}
let result = new Janken();
console.log(result.getNPCHand());
