# brunnock's solution

## to Queen Attack in the JavaScript Track

Published at Aug 19 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

In the game of chess, a queen can attack pieces which are on the same row, column, or diagonal.

A chessboard can be represented by an 8 by 8 array.

So if you're told the white queen is at (2, 3) and the black queen at (5, 6), then you'd know you've got a set-up like so:

``````_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ W _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ B _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
``````

You'd also be able to answer whether the queens can attack each other. In this case, that answer would be yes, they can, because both pieces share a diagonal.

## Setup

Go through the setup instructions for JavaScript to install the necessary dependencies:

http://exercism.io/languages/javascript/installation

## Running the test suite

The provided test suite uses Jasmine. You can install it by opening a terminal window and running the following command:

``````npm install -g jasmine
``````

Run the test suite from the exercise directory with:

``````jasmine queen-attack.spec.js
``````

In many test suites all but the first test have been marked "pending". Once you get a test passing, activate the next one by changing `xit` to `it`.

## Source

J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### queen-attack.spec.js

``````var Queens = require('./queen-attack');

describe('Queens', function () {
it('has the correct default positions', function () {
var queens = new Queens();
expect(queens.white).toEqual([0, 3]);
expect(queens.black).toEqual([7, 3]);
});

xit('initialized with specific placement', function () {
var queens = new Queens({white: [3, 7], black: [6, 1]});
expect(queens.white).toEqual([3, 7]);
expect(queens.black).toEqual([6, 1]);
});

xit('cannot occupy the same space', function () {
var positioning = {white: [2, 4], black: [2, 4]};

try {
var queens = new Queens(positioning);
expect(queens.white).toEqual([2, 4]);
expect(queens.black).toEqual([2, 4]);
} catch (error) {
expect(error).toEqual('Queens cannot share the same space');
}
});

xit('toString representation', function () {
var positioning = {white: [2, 4], black: [6, 6]};
var queens = new Queens(positioning);
var board = '_ _ _ _ _ _ _ _\n' +
'_ _ _ _ _ _ _ _\n' +
'_ _ _ _ W _ _ _\n' +
'_ _ _ _ _ _ _ _\n' +
'_ _ _ _ _ _ _ _\n' +
'_ _ _ _ _ _ _ _\n' +
'_ _ _ _ _ _ B _\n' +
'_ _ _ _ _ _ _ _\n'
;
expect(queens.toString()).toEqual(board);
});

xit('queens cannot attack', function () {
var queens = new Queens({ white: [2, 3], black: [4, 7] });
expect(queens.canAttack()).toEqual(false);
});

xit('queens can attack when they are on the same row', function () {
var queens = new Queens({ white: [2, 4], black: [2, 7] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack when they are on the same column', function () {
var queens = new Queens({ white: [5, 4], black: [2, 4] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack diagonally', function () {
var queens = new Queens({ white: [1, 1], black: [6, 6] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack another diagonally', function () {
var queens = new Queens({ white: [0, 6], black: [1, 7] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack yet another diagonally', function () {
var queens = new Queens({ white: [4, 1], black: [6, 3] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack on a north-east/south-west diagonal', function () {
var queens = new Queens({ white: [7, 0], black: [0, 7] });
expect(queens.canAttack()).toEqual(true);
});

xit('queens can attack on another ne/sw diagonal', function () {
var queens = new Queens({ white: [2, 6], black: [5, 3] });
expect(queens.canAttack()).toEqual(true);
});
});``````
``````class Queens {
constructor(pieces={white:[0,3], black:[7,3]}) {
if (typeof(pieces) === 'object') {
if (pieces.white.join('') === pieces.black.join('')) {
throw('Queens cannot share the same space');
} else {
this.white = pieces.white;
this.black = pieces.black;
}
}
this.board = Array(8).fill().map( ()=> Array(8).fill('_') );
this.board[this.white[0]][this.white[1]]='W';
this.board[this.black[0]][this.black[1]]='B';
}
toString() {
return (this.board.map( x=>x.join(' ')  ).join('\n') +'\n' );
}
canAttack() {
if (this.white[0] === this.black[0]) return (true);
if (this.white[1] === this.black[1]) return (true);
if ((this.white[0]-this.white[1]) === (this.black[0]-this.black[1])) return (true);
if ((this.white[0]+this.white[1]) === (this.black[0]+this.black[1])) return (true);
return(false);
}

}
module.exports = Queens;``````

### What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?