bst.js

const TreeNode = function (value) {
	this.left = null
	this.right = null
	this.value = value
}

// accept muliple sorted unqiue numbers arrays
const buildTreeNodes = function (...arrs) {
	let node = new TreeNode()
	for (let i = 0; i < arrs.length; i++) {
		for (let j = 0; j < arrs[i].length; j++) {
			addTreeNode(node, arrs[i][j])
		}
	}
	return node
}

const addTreeNode = function (node, value) {
	if (node.value == null) {
		node.value = value
	} else if (node.value > value) {
		if (!node.left) {
			node.left = new TreeNode(value)
		} else {
			addTreeNode(node.left, value)
		}
	} else if (node.value < value) {
		if (!node.right) {
			node.right = new TreeNode(value)
		} else {
			addTreeNode(node.right, value)
		}
	}
}

const readTreeNode = function (node) {
	let arr = []
	if (node) {
		if (node.left) {
			arr = arr.concat(readTreeNode(node.left))
		}
		arr.push(node.value)
		if (node.right) {
			arr = arr.concat(readTreeNode(node.right))
		}
	}
	return arr
}


const tree = buildTreeNodes([1, 12, 15, 26, 38], [2, 13, 17, 30, 45])

readTreeNode(node) //  [1, 2, 12, 13, 15, 17, 26, 30, 38, 45]