Use Map for node meta data.

src/data-structures/tree/BinaryTreeNode.js

@@ -3,14 +3,15 @@ import Comparator from '../../utils/comparator/Comparator';
 export default class BinaryTreeNode {
   /**
    * @param {*} [value] - node value.
-   * @param {Object} meta - any meta information that needs to be attached to the node.
    */
-  constructor(value = null, meta = {}) {
+  constructor(value = null) {
     this.left = null;
     this.right = null;
     this.parent = null;
     this.value = value;
-    this.meta = meta;
+
+    // Any node related meta information may be stored here.
+    this.meta = new Map();
 
     // This comparator is used to compare binary tree nodes with each other.
     this.nodeComparator = new Comparator();
@@ -157,29 +158,6 @@ export default class BinaryTreeNode {
     return traverse;
   }
 
-  /**
-   * @param {string} property
-   * @param {*} value
-   * @return {BinaryTreeNode}
-   */
-  setMeta(property, value) {
-    this.meta[property] = value;
-
-    return this;
-  }
-
-  /**
-   * @param property
-   * @return {*}
-   */
-  getMeta(property) {
-    if (!this.meta || !Object.prototype.hasOwnProperty.call(this.meta, property)) {
-      return null;
-    }
-
-    return this.meta[property];
-  }
-
   /**
    * @return {string}
    */