"once" event on specific layer throws an error

[cs09g]

mapbox-gl-js version:
v1.5.0

browser:
latest chrome

Steps to Trigger Behavior

1. add geojson layer
2. add once event on the layer
3. dispatch the event

Link to Demonstration

https://jsfiddle.net/cs09g/3rdf45ox/

Expected Behavior

the handler should be fired once.

Actual Behavior

error message in console

BTW, is once method deprecated? It's missing from API docs.

[kkaefer]

@cs09g the demo you linked doesn't include a callback function. That means the code that's trying to invoke the function fails. However, it looks like the linked JSFiddle might be incomplete. Can you check that it is indeed what you intended to post?

[cs09g]

@kkaefer oops, could you check the fiddle again? click the gray line on the map.

FYI, the missing code is

map.once("click", "route", (e) => {
  console.log(e);
});

[kkaefer]

The syntax allowing specifying the layer ID is only implemented for on, not for once. It's a little bit unfortunate since the Map object's on method overrides the Evented class' on method, inserting the layerId parameter in the middle. No such override exists for once, which is why it's not listed on the API documentation.

[ryanhamley]

There's an open PR to add this exact functionality if you'd like to give it a review @kkaefer. I worked on it with the author so I can't review it as well. #8875