# Insertion in binary search tree using recursion in typescript

Ts program for Insertion in binary search tree using recursion. Here more information.

```
// TypeScript program for
// Insertion in binary search tree by using recursion
class TreeNode
{
public data: number;
public left: TreeNode;
public right: TreeNode;
constructor(data: number)
{
this.data = data;
this.left = null;
this.right = null;
}
}
class BinarySearchTree
{
public root: TreeNode;
constructor()
{
this.root = null;
}
// Insert a node element
public TreeNode addNode(node: TreeNode, data: number)
{
if (node != null)
{
if (node.data >= data)
{
// When new element is smaller or
// equal to current node
node.left = this.addNode(node.left, data);
}
else
{
// When new element is higher to current node
node.right = this.addNode(node.right, data);
}
// important to manage root node
return node;
}
else
{
return new TreeNode(data);
}
}
// Display preorder
public preorder(node: TreeNode)
{
if (node != null)
{
// Display node value
console.log(" " + node.data);
// Visit to left subtree
this.preorder(node.left);
// Visit to right subtree
this.preorder(node.right);
}
}
public inorder(node: TreeNode)
{
if (node != null)
{
// Visit to left subtree
this.inorder(node.left);
// Display node value
console.log(" " + node.data);
// Visit to right subtree
this.inorder(node.right);
}
}
public postorder(node: TreeNode)
{
if (node != null)
{
// Visit to left subtree
this.postorder(node.left);
// Visit to right subtree
this.postorder(node.right);
// Display node value
console.log(" " + node.data);
}
}
public static main(args: string[])
{
var tree = new BinarySearchTree();
/*
10
/ \
/ \
4 15
/ \ /
3 5 12
-------------
Build binary search tree
*/
tree.root = tree.addNode(tree.root, 10);
tree.addNode(tree.root, 4);
tree.addNode(tree.root, 3);
tree.addNode(tree.root, 5);
tree.addNode(tree.root, 15);
tree.addNode(tree.root, 12);
// Display tree nodes
console.log("Preorder ");
tree.preorder(tree.root);
console.log("\nInorder ");
tree.inorder(tree.root);
console.log("\nPostorder ");
tree.postorder(tree.root);
}
}
BinarySearchTree.main([]);
/*
file : code.ts
tsc --target es6 code.ts
node code.js
*/
```

**Output**

```
Preorder
10
4
3
5
15
12
Inorder
3
4
5
10
12
15
Postorder
3
5
4
12
15
10
```

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