Write a function `deepFreeze(obj)` that deeply freezes an object so all nested properties are also immutable.
Problem Statement
<p>Write a function <code>deepFreeze(obj)</code> that deeply freezes an object so all nested properties are also immutable.</p>
Examples
Input: const obj = deepFreeze({ a: { b: 1 } }); obj.a.b = 2;
Output: obj.a.b remains 1
Explanation: All nested levels are frozen.
Complexity
Time Complexity: O(N)
Space Complexity: O(1)
Hints
š” Hint 1:
Object.freeze() only freezes top-level properties.
š” Hint 2:
Recursively freeze all object-type properties.
š” Hint 3:
Object.freeze(obj); Object.values(obj).forEach(val => { if (typeof val === "object" && val !== null) deepFreeze(val); });
Editorial & Approach
Problem Overview & Intuition
To solve Object.freeze Deep, we consider the execution characteristics of JavaScript engines. Write a function `deepFreeze(obj)` that deeply freezes an object so all nested properties are also immutable. By utilizing idiomatic language constructs and clean algorithmic principles, we can accomplish this with optimal time and memory usage.
Step-by-Step Approach
- Understand Problem Contract: Identify input arguments, return type expectations, and edge cases (empty inputs, nullish values).
- Choose Core Mechanism: Use modern JavaScript patterns (object.freeze() only freezes top-level properties).
- Implement Logic: Handle state and transformations efficiently (recursively freeze all object-type properties).
- Return Result: Ensure proper return format and preserve caller context if applicable.
Optimal Implementation (JavaScript)
function deepFreeze(obj) {
Object.freeze(obj);
Object.values(obj).forEach(val => {
if (typeof val === "object" && val !== null && !Object.isFrozen(val)) {
deepFreeze(val);
}
});
return obj;
}Complexity Analysis
Time Complexity
O(N) linear scan over input
Space Complexity
O(1) constant auxiliary space (or O(N) output)
Edge Cases & Corner Traps Handled
- Empty or boundary inputs (empty arrays, strings, zero length).
- Type checks and unexpected values (e.g.
null,undefined, negative numbers). - Closure preservation and memory isolation between separate invocations.