Method once

src/common/util/MapExtend.js:194–196

(type, layerId, listener)

    }

    once(type, layerId, listener) {
      return this._eventsModeHandler({ type, layerId, listener, mode: 'once' });
    }

    off(type, layerId, listener) {
      return this._eventsModeHandler({ type, layerId, listener, mode: 'off' });