JavaScript Snippet

Throttle with Leading and Trailing Edges

Difficulty: Hard

A leading-only throttle drops the last call's arguments; a trailing-only throttle feels laggy on the first event. The Lodash-style throttle that fires on BOTH edges is the version every UI codebase eventually wants: an immediate response on the leading edge plus a guaranteed final fire after the burst ends. This snippet builds that production-grade throttle from scratch with cancel and flush, then shows the configurable `leading` / `trailing` toggle that powers most real-world helpers.