link.distance()

link.distance([distance])

If distance is specified, sets the distance accessor to the specified number or function, re-evaluates the distance accessor for each link, and returns this force. If distance is not specified, returns the current distance accessor, which defaults to:

function distance() {
  return 30;
}

The distance accessor is invoked for each link, being passed the link and its zero-based index. The resulting number is then stored internally, such that the distance of each link is only recomputed when the force is initialized or when this method is called with a new distance, and not on every application of the force.