kthSmallest.js

var kthSmallest = function(binaryTree, k) {
	var arr = [];
	var search = function(tree) {	
		if (arr.length<k) {
			arr.push(tree.value)
			search(tree.left);
			search(tree.right);
		} else {
			if (tree.value < Math.max(arr)) {
				arr.splice(arr.indexOf(Math.max(arr)));
				arr.push(tree.value);
				search(tree.left);
				search(tree.right);
			}
		}
	}
	search(binaryTree);
	return Math.max(arr);

}

var kthSmallest = function(tree, k) {
	if (tree.children === null) {
		return tree.value
	} else {
		return Array.reduce([kthSmallest(tree.left), tree.value, kthSmallest(tree.right)], function(acc, next) {
			if (acc>next && acc[0]<k) {
				acc[0]++;
				acc[1] = y;

			}
		})
	}
}