Initial data commit

Task/Galton-box-animation/JavaScript/galton-box-animation.js

@@ -0,0 +1,126 @@
+const readline = require('readline');
+
+/**
+ * Galton Box animation
+ * @param {number} layers The number of layers in the board
+ * @param {number} balls The number of balls to pass through
+ */
+const galtonBox = (layers, balls) => {
+  const speed = 100;
+  const ball = 'o';
+  const peg = '.';
+  const result = [];
+
+  const sleep = ms => new Promise(resolve => {
+    setTimeout(resolve,ms)
+  });
+
+  /**
+   * The board is represented as a 2D array.
+   * @type {Array<Array<string>>}
+   */
+  const board = [...Array(layers)]
+      .map((e, i) => {
+        const sides = Array(layers - i).fill(' ');
+        const a = Array(i + 1).fill(peg).join(' ').split('');
+        return [...sides, ...a, ...sides];
+      });
+
+  /**
+   * @return {Array<string>}
+   */
+  const emptyRow = () => Array(board[0].length).fill(' ');
+
+  /**
+   * @param {number} i
+   * @returns {number}
+   */
+  const bounce = i => Math.round(Math.random()) ? i - 1 : i + 1;
+
+  /**
+   * Prints the current state of the board and the collector
+   */
+  const show = () => {
+    readline.cursorTo(process.stdout, 0, 0);
+    readline.clearScreenDown(process.stdout);
+    board.forEach(e => console.log(e.join('')));
+    result.reverse();
+    result.forEach(e => console.log(e.join('')));
+    result.reverse();
+  };
+
+
+  /**
+   * Collect the result.
+   * @param {number} idx
+   */
+  const appendToResult = idx => {
+    const row = result.find(e => e[idx] === ' ');
+    if (row) {
+      row[idx] = ball;
+    } else {
+      const newRow = emptyRow();
+      newRow[idx] = ball;
+      result.push(newRow);
+    }
+  };
+
+  /**
+   * Move the balls through the board
+   * @returns {boolean} True if the there are balls in the board.
+   */
+  const iter = () => {
+    let hasNext = false;
+    [...Array(bordSize)].forEach((e, i) => {
+      const rowIdx = (bordSize - 1) - i;
+      const idx = board[rowIdx].indexOf(ball);
+      if (idx > -1) {
+        board[rowIdx][idx] = ' ';
+        const nextRowIdx = rowIdx + 1;
+        if (nextRowIdx < bordSize) {
+          hasNext = true;
+          const nextRow = board[nextRowIdx];
+          nextRow[bounce(idx)] = ball;
+        } else {
+          appendToResult(idx);
+        }
+      }
+    });
+    return hasNext;
+  };
+
+  /**
+   * Add a ball to the board.
+   * @returns {number} The number of balls left to add.
+   */
+  const addBall = () => {
+    board[0][apex] = ball;
+    balls = balls - 1;
+    return balls;
+  };
+
+  board.unshift(emptyRow());
+  result.unshift(emptyRow());
+
+  const bordSize = board.length;
+  const apex = board[1].indexOf(peg);
+
+  /**
+   * Run the animation
+   */
+  (async () => {
+    while (addBall()) {
+      await sleep(speed).then(show);
+      iter();
+    }
+    await sleep(speed).then(show);
+    while (iter()) {
+      await sleep(speed).then(show);
+    }
+    await sleep(speed).then(show);
+  })();
+
+
+};
+
+galtonBox(12, 50);