数组转换为嵌套的Json

function arrayToNestedJson(arr) {
  var json = {};
  
  for (var i = 0; i < arr.length; i++) {
    var element = arr[i];
    
    if (Array.isArray(element)) {
      json[i] = arrayToNestedJson(element);
    } else {
      json[i] = element;
    }
  }
  
  return json;
}

var array = [1, 2, [3, 4, [5, 6]]];
var nestedJson = arrayToNestedJson(array);
console.log(JSON.stringify(nestedJson));

{
  "0": 1,
  "1": 2,
  "2": {
    "0": 3,
    "1": 4,
    "2": {
      "0": 5,
      "1": 6
    }
  }
}