WPT details: This feature added the GamepadHapticActuator.effects array and the test below checks for its presence. https://wpt.fyi/results/gamepad/idlharness.window.html?label=experimental&label=master&aligned However, currently there isn't a way to actually check the effects array contents or to check whether a trigger-rumble effect has been played, as it requires a gamepad device.
Extend the GamepadHapticActuator interface to expose the trigger-rumble capability in the Web for compatible gamepads. This extension will allow web applications that take advantage of the Gamepad API to also vibrate the triggers of gamepad devices that come equipped with this functionality.
Xbox-compatible gamepads like the Microsoft Xbox Wireless Controller and Razer Wolverine Ultimate come equipped with "impulse triggers" which provide haptic feedback localized to the triggers. While the Gamepad Haptics Extension proposal already provides support for haptic effects that vibrate the whole gamepad, it does not expose an interface for issuing "impulse trigger" effects.
Samples: https://nondebug.github.io/gamepad-explorer
Explainers: https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/GamepadHapticsActuatorTriggerRumble/explainer.md