Question

below is my code. I want that Player1,2 will be objects of proto RPSPlayer and that each one would have separate ‘history’ array. But now, somehow every time i run Player1.play() and Player2.play() they both updates the same ‘history’ array and shares it. Thanks!

function RPSPlayer() {}
    RPSPlayer.prototype.numOfWins = 0;
    RPSPlayer.prototype.history = [];
    RPSPlayer.prototype.myCurrPick;
    RPSPlayer.prototype.getW = function () {return this.numOfWins;};
    RPSPlayer.prototype.choose = function (item) {
        this.history.push(item);
 };

Player1 = new RPSPlayer();
Player1.play = function(){
    var randomnumber=Math.floor(Math.random()*3);
    if(randomnumber==0){this.currPick = "rock";}
    else if(randomnumber==1){this.currPick = "paper";}
    else{this.currPick = "scissors";}
    this.choose(this.currPick);
    return this.currPick;
};

Player2 = new RPSPlayer();
Player2.play = function(){
    this.choose("rock");
    this.currPick = "rock";
    return "rock";
};

Answer 1

You have to initialize instance properties in the constructor:

function RPSPlayer() {
    this.history = [];
}

Every value assigned to a property of RPSPlayer.prototype is shared among all instances (which is one of the purposes of the prototype).