Map With History

Requirements

• Export MapWithHistory<K,V> as named and default. set(key, value, timestamp) stores a version and returns this. get(key, timestamp) returns the value at the greatest recorded timestamp less than or equal to the query, or undefined if no such version exists.
• Omit timestamp in get/has to query the latest version. Explicit positive Infinity is also allowed for queries. has(key, timestamp) reports whether an eligible version exists, even when its stored value is undefined.
• Writes may arrive in any timestamp order. A write at an already-recorded timestamp replaces that timestamp’s value; newer arrival does not otherwise override later timestamps. Keys follow native Map identity/equality behavior. Different keys and instances have independent histories.
• Write timestamps must be finite numbers. Query timestamps must be finite numbers or positive Infinity. Negative and fractional finite timestamps are valid. Invalid timestamps throw TypeError and must not modify existing history.
• Use binary search to locate writes and reads in per-key sorted histories. Reads should be O(log v) for v versions under one key; writes may be O(v) due to array insertion. Store values by reference; do not clone or mutate them.
• No deletion, expiration, persistent storage, wall-clock sampling, iteration API, or time-zone conversion is needed. TypeScript get returns V | undefined and supports generic key/value types.

Examples

Input: const m = new MapWithHistory(); m.set("theme", "light", 10).set("theme", "dark", 20);
m.get("theme", 15); m.get("theme");
Output: "light" and "dark"

Input: m.set("theme", "contrast", 12); m.get("theme", 15);
Output: "contrast"