UNDOs for your clojurescript projects.
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Historian logo

"The present is the least important time we live in" --Alan Kay

A drop-in atom-state-management (UNDOs!!) for your clojurescript projects.

Also supports clojure in case you would want to make similar applications, or simply for testing.

Table of contents

Replacing Historian atoms


Add the following dependency in your project.clj:

Clojars Project

And require historian in your namespace:

(ns my-ns
  (:require [historian.core :as hist]))

Suppose you have your state in an atom my-state:

(def my-state (atom "ABC"))

To keep an history of all changes, simply add your atom to historian:

(hist/record! my-state :my-state)

;; then change the state of your atom

(reset! my-state "DEF")

=> "DEF"


=> "ABC"


=> "DEF"

;; tada!

Of course, sometimes we want to do some things without anyone noticing...

;; our current state is "ABC"

 (reset! my-state "GHI"))  ;; <--- this change won't be added to the undo history

(reset! my-state "ZZZ")


=> "ABC"

If you have a bunch of operations initiated by a single user action:

 (doseq [i (range 200)]
  (reset! my-state i)))
;; We've just done 200 operations on the atom, but only the last state is recorded.


=> "ABC"

To check if any undo/redo history is available, use can-undo? and can-redo?.

When loading an app with multiple atoms, you should use clear-history! and trigger-record! to start with a clean slate.

Keyboard Shortcuts (cljs)

You can bind ctrl-z and ctrl-y to undo and redo by using bind-keys in the historian.keys namespace.

Replacing Atoms

You might need to replace the atoms in which Historian stores its data. (Say, for example, to make them compatible with Reagent).

(ns some-ns (:require [reagent.core :refer [atom]]
                      [historian.core :as hist]))

;; for undos:
(hist/replace-library! (atom [])) ; <----- the new atom must be a vector.

;; for redos:
(hist/replace-prophecy! (atom [])) ; <----- the new atom must be a vector.