files/en-us/web/api/sensor/activate_event/index.md
{{securecontext_header}}{{APIRef("Sensor API")}}
The activate event is fired when a sensor becomes activated. It means that it will start obtaining readings.
The {{domxref('Sensor')}} interface is a base class, onactivate and the activate event may only be used
on one of the derived classes.
Use the event name in methods like {{domxref("EventTarget.addEventListener", "addEventListener()")}}, or set an event handler property.
addEventListener("activate", (event) => { })
onactivate = (event) => { }
A generic {{domxref("Event")}} with no added properties.
This example adds an event listener to log the activation of an {{domxref("Accelerometer")}}.
const acl = new Accelerometer({ frequency: 60 });
acl.addEventListener("activate", () => console.log("Ready to measure."));
acl.start();
{{Specifications}}
{{Compat}}