The same Waypoint instance, allowing chained method calls.
Enables the waypoint, allowing the handler function to trigger.
By default, waypoints are enabled and calling this function will do nothing. However, if you previously disabled a waypoint by calling the disable method or passing
enabled: false as an option when creating the waypoint, calling this method will renable the waypoint. A disabled waypoint's handler is not triggered when it is crossed. If the waypoint was crossed while it was disabled those triggers do not accumulate and fire when renabled. They are lost. This is the point of disabling.
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