gistfile1.js

app.get('/move/:from/:to', function(req, res) {
  console.log("Move");
  // Define the 'board' parameter here.
  board.load(function(board) {
    from = req.params.from
    to = req.params.to
    // The scope of `this is far too finicky, it's always better to
    // try another option if you can. In this case
    res.send({removed: board.move(from, to)})
  });
});

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board.js

var fs = require('fs');

module.exports = {
  pieces: {}

  , create: function () {
    this.buildBackRow("1", "W");
    this.buildPawnRow("2", "W");
    for (var col = 3; col <= 6; col ++) {
      this.buildBlankRow(col)
    }
    this.buildPawnRow("7", "B");
    this.buildBackRow("8", "B");
    this.save();
    return this.pieces;
  }

  , buildBackRow: function (row, color) {
    for (var col = 0; col < 8; col ++) {
      this.pieces[this.col_labels[col] + row] = color + this.row_pieces[col];
    }
  }

  , buildPawnRow: function (row, color) {
    for (var col = 0; col < 8; col ++) {
      this.pieces[this.col_labels[col] + row] = color + "P";
    }
  }

  , buildBlankRow: function (row) {
    for (var col = 0; col < 8; col ++) {
      this.pieces[this.col_labels[col] + row] = "";
    }
  }
  , col_labels: ["a", "b", "c", "d", "e", "f", "g", "h"]
  , row_pieces: ["R", "N", "B", "Q", "K", "B", "N", "R"]
  , save: function () {
    fs.writeFileSync("board.hash", JSON.stringify(this.pieces));
  }
  , load: function (callback) {
    fs.readFile('board.hash', function(err, data) {
      if (err) {
        console.log("Missing");
        this.pieces = {};
      }
      else {
        this.pieces = JSON.parse(data);
      }
      // Pass in the board to the callback, so that it can work on it.
      // This will become the `board` parameter up the top.
      callback(this);
    });
  }
  , move: function (from, to) {
    console.log("here");
    piece = this.pieces[from]
    this.pieces[from] = "";
    removed = this.pieces[to]
    this.pieces[to] = piece;
    return removed;
  }
};