Basic Nim game vs computer in JavaScript

This is my first time writing a basic program/game in any programming language.
It is supposed to a be a Nim game vs a computer with these basic parameters:

• Use prompt() to prompt moves and input.

• Use console.log() draw the board.

The board should look like this:


Pile A: ooooo


Pile B: ooo


Pile C: ooooo

It has been very difficult for me to approach this problem, and I know the logic that I have used is very basic and buggy. Any pointers would be appreciated, whether in the code or my approach to solving the problem in general.

```
var pileA = {
circles: "ooooo",
print: function() {
console.log("Pile A: " + this.circles);
}
};

var pileB = {
circles: "ooooo",
print: function() {
console.log("Pile B: " + this.circles);
}
};

var pileC = {
circles: "ooooo",
print: function() {
console.log("Pile C: " + this.circles);
}
};

function printBoard(){
console.log("** Nim **");
pileA.print();
pileB.print();
pileC.print();
}

function yourMove(){

printBoard();

var moveData = prompt("Type letter of pile and # of o's you are removing.\n" +
"Ex. A1 or C4");

if (moveData[0] == 'A') {
var x = pileA.circles.length - moveData[1];
pileA.circles = pileA.circles.slice(0,x);
return pileA.circles;
} else if (moveData[0] == 'B') {
var x = pileB.circles.length - moveData[1];
pileB.circles = pileB.circles.slice(0,x);
return pileB.circles;
} else if (moveData[0] == 'C') {
var x = pileC.circles.length - (moveData[1]+1);
pileC.circles = pileC.circles.slice(0,x);
return pileC.circles;
}

}

function computersMove() {

printBoard();

alert("Now it is the computer's turn!");

if (pileA.circles != "") {
pileA.circles = pileA.circles.slice(0,0);
return pileA.circles;
} else if (pileB.circles != "") {
pileB.c

I stumbled across this because a friend told me he got hit with this question recently for a coding bootcamp entrance exam. I had to look and see what it is, of course : )

Josh has a great answer with excellent use of higher order functions and keeping things DRY. At a glance, one change that I'd make with his code is the usage of the reduce function. It's a bit verbose and possibly difficult for a beginner to parse through. A clearer declaration would be using something like Array.every (once all the circles return an empty string "", the GameOver function returns true). It's a tiny gripe, but it's more intuitive. The usage would be substituted like this:

function isGameOver() {
  return piles.every(function(pile) {
    return pile.circles === "";
  });
}

StackExchange Code Review Q#132674, answer score: 2