Add binary search tree.

src/data-structures/tree/binary-search-tree/BinarySearchTree.js

@@ -0,0 +1,19 @@
+import BinarySearchTreeNode from './BinarySearchTreeNode';
+
+export default class BinarySearchTree {
+  constructor() {
+    this.root = new BinarySearchTreeNode();
+  }
+
+  insert(value) {
+    this.root.insert(value);
+  }
+
+  contains(value) {
+    return this.root.contains(value);
+  }
+
+  toString() {
+    this.root.toString();
+  }
+}

src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

@@ -0,0 +1,38 @@
+import BinaryTreeNode from '../BinaryTreeNode';
+
+export default class BinarySearchTreeNode extends BinaryTreeNode {
+  insert(value) {
+    if (value < this.value) {
+      // Insert to the left.
+      if (this.left) {
+        this.left.insert(value);
+      } else {
+        this.left = new BinarySearchTreeNode(value);
+      }
+    } else {
+      // Insert to the right.
+      if (this.right) {
+        this.right.insert(value);
+      } else {
+        this.right = new BinarySearchTreeNode(value);
+      }
+    }
+
+    return this;
+  }
+
+  contains(value) {
+    // Check the root.
+    if (this.value === value) {
+      return true;
+    }
+
+    if (value < this.value && this.left) {
+      return this.left.contains(value);
+    } else if (this.right) {
+      return this.right.contains(value);
+    }
+
+    return false;
+  }
+}

src/data-structures/tree/binary-search-tree/__test__/BinarySearchTree.test.js

@@ -0,0 +1,5 @@
+describe('BinarySearchTree', () => {
+  it('should create binary search tree', () => {
+
+  });
+});

src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js

@@ -0,0 +1,44 @@
+import BinarySearchTreeNode from '../BinarySearchTreeNode';
+
+describe('BinarySearchTreeNode', () => {
+  it('should create binary search tree', () => {
+    const bstNode = new BinarySearchTreeNode(2);
+
+    expect(bstNode.value).toBe(2);
+    expect(bstNode.left).toBeNull();
+    expect(bstNode.right).toBeNull();
+  });
+
+  it('should insert nodes in correct order', () => {
+    const bstNode = new BinarySearchTreeNode(2);
+    bstNode.insert(1);
+
+    expect(bstNode.toString()).toBe('1,2');
+    expect(bstNode.contains(1)).toBeTruthy();
+    expect(bstNode.contains(3)).toBeFalsy();
+
+    bstNode.insert(3);
+
+    expect(bstNode.toString()).toBe('1,2,3');
+    expect(bstNode.contains(3)).toBeTruthy();
+    expect(bstNode.contains(4)).toBeFalsy();
+
+    bstNode.insert(7);
+
+    expect(bstNode.toString()).toBe('1,2,3,7');
+    expect(bstNode.contains(7)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+
+    bstNode.insert(4);
+
+    expect(bstNode.toString()).toBe('1,2,3,4,7');
+    expect(bstNode.contains(4)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+
+    bstNode.insert(6);
+
+    expect(bstNode.toString()).toBe('1,2,3,4,6,7');
+    expect(bstNode.contains(6)).toBeTruthy();
+    expect(bstNode.contains(8)).toBeFalsy();
+  });
+});