JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {"1":[],"css":{"admin":[],"tabs":{"skin1":{"images":[]},"skin10":{"images":[]},"skin11":{"images":[]},"skin12":{"images":[]},"skin2":[],"skin3":{"images":[]},"skin4":{"images":[]},"skin5":{"images":[]},"skin6":{"images":[]},"skin7":{"images":[]},"skin8":{"images":[]},"skin9":{"images":[]}}},"img":{"admin":[],"filemanager":[],"icons":[]},"js":{"libs":[]},"menu":{"img":[]},"walpappere":{"1":[]}};

function list(items, level) {
 for(var key in items) {
  document.write(
      (new Array(level + 1)).join(" ")
      + key
      + "<br>");
  if(typeof items[key] === "object") {
   list(items[key], level + 1);
  }
 }
}

list(obj, 0);