Object Descriptors & Property Flags

What's the key difference between these two functions?

function shallowFreeze(obj) {
  Object.freeze(obj);
  return obj;
}

function deepFreeze(obj) {
  // Freeze properties before freezing self
  Object.keys(obj).forEach(prop => {
    if (
      obj[prop] !== null &&
      (typeof obj[prop] === 'object' || typeof obj[prop] === 'function') &&
      !Object.isFrozen(obj[prop])
    ) {
      deepFreeze(obj[prop]);
    }
  });
  
  return Object.freeze(obj);
}

shallowFreeze is faster
deepFreeze recursively freezes nested objects
The key difference is that deepFreeze recursively freezes nested objects: 1) shallowFreeze only freezes the top-level object properties, leaving nested objects mutable, 2) deepFreeze recursively traverses the object graph and freezes all nested objects, 3) It checks each property, and if it's an object or function, freezes it recursively, 4) It handles cycles by checking if objects are already frozen, 5) This creates true immutability throughout the entire object structure, 6) It's significantly more thorough but also more performance-intensive, 7) This pattern is essential when working with complex object graphs that need complete protection from modification.
deepFreeze works with functions
shallowFreeze doesn't actually freeze objects

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