lock

What it does

Alias of snapshot() kept for backward compatibility (pre-v3 name). lock and snapshot share the same implementation at runtime — export const lock = snapshot.

When to use

Use snapshot for new code. Use lock only when migrating code that already calls lock() and you want to defer the rename.

When not to use

Same restrictions as snapshot. Do not use for non-cloneable values (functions, Symbols, DOM nodes).

Guarantees

Identical to snapshot: deep clone via structuredClone, null-prototype severance on plain objects (S1), full deepFreeze on the clone, and DeepReadonly<T> return type.

Limitations

Same as snapshot.

Example

import { lock } from 'constancy';

const state = { count: 0 };
const frozen = lock(state);

state.count++;         // original mutated
frozen.count;          // 0 — snapshot unaffected
frozen.count = 1;      // TypeError — frozen

Comparison with related APIs

lock is snapshot — see snapshot — Comparison.

Common mistakes

Using lock in new code creates unnecessary confusion with the v3 snapshot name. Prefer snapshot in all new code.

Type signature

const lock: <T>(value: T) => DeepReadonly<T>

See also

• snapshot — canonical name; identical implementation
• Migration guide — rename guide for pre-v3 code