invert binary tree

invert.js

function invert(tree) {
  if (!tree instanceof Array || tree.length === 1) return tree;

  var ret = [];
  var inverted = tree.reverse();

  for(var cur in inverted) {
    if(!inverted.hasOwnProperty(cur)) continue;
    ret.push(inverted[cur] instanceof Array ? invert(inverted[cur]) : inverted[cur]);
  }
  
  return ret;
}

var tree = [[['a'], 'b', ['c', 'd', null]], 'f', [['g'], 'h', ['i']]];

console.log(invert(tree));
// [ [ [ 'i' ], 'h', [ 'g' ] ], 'f', [ [ null, 'd', 'c' ], 'b', [ 'a' ] ] ]

invert_es5.js

'use strict';

function invert(tree) {
  if (!tree instanceof Array || tree.length === 1) return tree;
  
  return tree.reverse().map(function (cur) {
    return Array.isArray(cur) ? invert(cur) : cur; 
  });
}

var tree = [[['a'], 'b', ['c', 'd', null]], 'f', [['g'], 'h', ['i']]];

console.log(invert(tree));
// [ [ [ 'i' ], 'h', [ 'g' ] ], 'f', [ [ null, 'd', 'c' ], 'b', [ 'a' ] ] ]