How to check if a binary tree is balanced in JavaScript

Binary Tree, JavaScript, Trees, algorithms

Here is one way to check whether a binary tree is balanced:

Time complexity: O(n).
Space complexity: O(h) where h is height because of recursion and call stack requirements

checkBalancedTry in REPL
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// A balanced tree is defined as a tree where the height of the two subtrees of any node never differ by more than one.
function checkHeight(root) {
  if (!root) return -1;
  
  const leftHeight = checkHeight(root.left);
  if (leftHeight === -Infinity) return -Infinity;
  
  const rightHeight = checkHeight(root.right);
  if (rightHeight === -Infinity) return -Infinity;
  
  const heightDiff = Math.abs(leftHeight - rightHeight);
  return heightDiff > 1 ? -Infinity : Math.max(leftHeight, rightHeight) + 1;
}
function checkBalanced(root) {
  return checkHeight(root) !== -Infinity;
}
function Tree(value) {
    this.value = value;
    this.left = null;
    this.right = null;
}

Tests can be found at REPL.it