make object immutable

freeze.js

"use strict";
function freeze(obj) {
  if(typeof obj !== "object") {
   return;
  }
  Object.freeze(obj);
    
  for (let prop in obj) {
   if (obj.hasOwnProperty(prop)) {
    freeze(obj[prop]);
   }
  }
}

let obj = { a: 5, nested: { b: 6, arr: [1, 2] } };
freeze(obj);
//obj.a = 7; // --> TypeError
//obj.nested = null; // --> TypeError
//obj.nested.b = -5; // --> TypeError
//obj.c = "new prop"; // --> TypeError
obj.nested.arr.push(13); // --> TypeError