A binary search tree that stays sorted

A binary search tree keeps every value smaller than a node in its left subtree and every larger value in its right, so an in-order walk emerges sorted and a lookup only ever follows one path down.

Implement a BST class holding numbers. It is constructed with no arguments and starts empty. insert(value) adds a number and returns true, or returns false and changes nothing if that number is already in the tree. has(value) returns true or false. inOrder() returns an array of the stored numbers in ascending order, and [] when empty. size() returns how many distinct numbers are stored. min() and max() return the smallest and largest stored numbers, or undefined when the tree is empty.

const t = new BST();
[8, 3, 10, 1, 6, 14].forEach((v) => t.insert(v));
t.inOrder();  // [1, 3, 6, 8, 10, 14]
t.min();      // 1
t.max();      // 14

const t = new BST();
t.insert(5);  // true
t.insert(5);  // false — duplicate
t.has(5);     // true
t.has(99);    // false