Initialise a simple binary tree in a terse way - Javascript

binary-tree-terse.js

"use strict";


class TreeNode {
  data;
  left;
  right;  
  
  constructor(data) {
    this.data = data;
  }
}

const leftRight = {0: "left", 1: "right"}

// const tree = [
//        [1],
//    [2,      3],
//  [n,  4,   5,   6],
//  [   n,n, 7,8, n,n]
// ]
function makeBinaryTree (structure) {
  let root = new TreeNode(structure.shift()[0]);
  let parents = [root]

  for (const row of structure) {
    parents = row.reduce((arr, v, i) => {
      if (v !== null) {
        const node = new TreeNode(v);
        parents[Math.floor(i / 2)][leftRight[i % 2]] = node;        
        arr.push(node);
      }
      
      return arr;
    }, []) 
  }

  return root;
}


const n = null;
const tree = [
       [1],
   [2,      3],
 [n,  4,   5,   6],
 [   n,n, 7,8, n,n]
]


console.log(makeBinaryTree(tree))

// TreeNode {
//   data: 1,
//   left: TreeNode {
//     data: 2,
//     left: undefined,
//     right: TreeNode { data: 4, left: undefined, right: undefined }
//   },
//   right: TreeNode {
//     data: 3,
//     left: TreeNode { data: 5, left: [TreeNode], right: [TreeNode] },
//     right: TreeNode { data: 6, left: undefined, right: undefined }
//   }
// }