Initial data commit

Task/Generate-random-chess-position/JavaScript/generate-random-chess-position.js

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+Array.prototype.shuffle = function() {
+  for (let i = this.length - 1; i > 0; i--) {
+    let j = Math.floor(Math.random() * (i + 1));
+    [this[i], this[j]] = [this[j], this[i]];
+  }
+}
+
+function randomFEN() {
+
+  let board = [];
+  for (let x = 0; x < 8; x++) board.push('. . . . . . . .'.split(' '));
+
+  function getRandPos() {
+    return [Math.floor(Math.random() * 8), Math.floor(Math.random() * 8)];
+  }
+
+  function isOccupied(pos) {
+    return board[pos[0]][pos[1]] != '.';
+  }
+
+  function isAdjacent(pos1, pos2) {
+    if (pos1[0] == pos2[0] || pos1[0] == pos2[0]-1 || pos1[0] == pos2[0]+1)
+    if (pos1[1] == pos2[1] || pos1[1] == pos2[1]-1 || pos1[1] == pos2[1]+1)
+      return true;
+    return false;
+  }
+
+  // place kings
+  let wk, bk;
+  do { wk = getRandPos(); bk = getRandPos(); }
+  while (isAdjacent(wk, bk));
+  board[wk[0]][wk[1]] = 'K';
+  board[bk[0]][bk[1]] = 'k';
+
+  // get peaces
+  let peaces = [];
+  let names = 'PRNBQ';
+  function pick() {
+    for (x = 1; x < Math.floor(Math.random() * 32); x++)
+      peaces.push(names[Math.floor(Math.random() * names.length)]);
+  }
+  pick();
+  names = names.toLowerCase();
+  pick();
+  peaces.shuffle();
+
+  // place peaces
+  while (peaces.length > 0) {
+    let p = peaces.shift(), pos;
+    // paws: cannot be placed in bottom or top row
+    if (p == 'p' || p == 'P')
+      do { pos = getRandPos() }
+      while (isOccupied(pos) || pos[0] == 0 || pos[0] == 7);
+    // everything else
+    else do { pos = getRandPos(); } while (isOccupied(pos));
+    board[pos[0]][pos[1]] = p;
+  }
+
+  // write FEN
+  let fen = [];
+  for (x = 0; x < board.length; x++) {
+    let str ='', buf = 0;
+    for (let y = 0; y < board[x].length; y++)
+      if (board[x][y] == '.') buf++;
+      else {
+        if (buf > 0) { str += buf; buf = 0; }
+        str += board[x][y];
+      }
+    if (buf > 0) str += buf;
+    fen.push(str);
+  }
+  fen = fen.join('/') + ' w - - 0 1';
+  console.table(board); // for demonstrating purpose
+  return fen;
+}
+
+// example
+console.log(randomFEN());