2019-3-28

class Node {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
  insert(data) {
    if (data < this.data && this.left) {
      this.left.insert(data);
    } else if (data < this.data) {
      this.left = new Node(data);
    } else if (data > this.data && this.right) {
      this.right.insert(data);
    } else if (data > this.data) {
      this.right = new Node(data);
    }
  }
}
// to be valid, node should satisfy min and max ALONGSIDE with all his children
// first we check if node data satisfying min and max
// then we do recursive check for node left and right children
function validate(node, min = null, max = null) {
  const { left, right, data } = node;
  // node is invalid when doesn't satisfy min or max
  if ((max && data > max) || (min && data < min)) return false;
  // true by default, since if node doesn't have a child, it should be accepted as valid
  let isLeftChildValid = true;
  let isRightChildValid = true;
  if (left) isLeftChildValid = validate(left, min, data);
  if (right) isRightChildValid = validate(right, data, max);
  // at this step node validity depends on validity of his children
  // because all check of node data itself was made above (line 8)
  return isLeftChildValid && isRightChildValid;
}

// --- Directions
// Create an 'eventing' library out of the
// Events class.  The Events class should
// have methods 'on', 'trigger', and 'off'.
class Events {
  constructor() {
    this.event = {}
  }
  // Register an event handler
  on(eventName, callback) {
    if (this.event.hasOwnProperty(eventName)) {
      this.event[eventName].push(callback);
    } else {
      this.event[eventName] = [callback];
    }
  }
  // Trigger all callbacks associated
  // with a given eventName
  trigger(eventName) {
    if (!this.event.hasOwnProperty(eventName)) return;
    for (let cb of this.event[eventName]) {
      cb();
    }
  }
  // Remove all event handlers associated
  // with the given eventName
  off(eventName) {
    delete this.event[eventName];
  }
}

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