It's not currently possible. You would need to store the the current value somewhere (on window, or Bokeh, or wherever else that is convenient) and then refer to that as the "last" value in a subsequent call.
On Jul 29, 2018, at 03:57, phuebu via Bokeh Discussion - Public <[email protected]> wrote:
When using callbacks from on_change we get given both the old value and the new value of the attribute which has changed.
Is it also possible to get the old value of an attribute when using CustomJS callbacks?
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