Throttle

Implement throttle(fn, wait). Invoke immediately when idle, then at most once per wait milliseconds, retaining the latest call for trailing execution.

Requirements

Leading and trailing: invoke immediately when idle; calls during cooldown replace pending work. Each trailing invocation starts another cooldown. Never duplicate a single leading call.

Preserve executed call arguments and this.

Attach cancel() to clear pending work and reset the wrapper for reuse.

Each wrapper maintains independent state and returns undefined.

Assume a synchronous non-reentrant callback and a finite positive wait. No flush, maxWait, or configurable options are required.

throttle(fn, wait) returns a callable with cancel(). TypeScript preserves argument and receiver types.

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"advance","milliseconds":50},{"type":"call","arguments":[2]},{"type":"advance","milliseconds":250}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null},{"at":100,"arguments":[2],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1],"context":{"label":"first"}},{"type":"call","arguments":[2],"context":{"label":"last"}},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":"first"},{"at":100,"arguments":[2],"context":"last"}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"call","arguments":[2]},{"type":"cancel"},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"cancel"},{"type":"call","arguments":[2]},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null},{"at":0,"arguments":[2],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"advance","milliseconds":200},{"type":"call","arguments":[2]},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null},{"at":200,"arguments":[2],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[]},{"type":"advance","milliseconds":200}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[],"context":null}],"pendingTimers":0}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"advance","milliseconds":99}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null}],"pendingTimers":1}

Input arguments: {"delay":100,"actions":[{"type":"call","arguments":[1]},{"type":"call","arguments":[2]},{"type":"advance","milliseconds":110},{"type":"call","arguments":[3]},{"type":"advance","milliseconds":290}]} Expected: {"returnedFunction":true,"hasCancel":true,"calls":[{"at":0,"arguments":[1],"context":null},{"at":100,"arguments":[2],"context":null},{"at":200,"arguments":[3],"context":null}],"pendingTimers":0}

Requirements

Examples