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createAtom(val[, plugin]) => AtomInstance

Creates a new atom instance.


  • val: The initial stored value within the atom
  • plugin (optional): A function that returns a read and write method, with the same semantics described in the AtomInstance API. If plugin is not supplied, the default in-memory storage interface is used.

An interface for external persistence

Your atom doesn't necessarily have to be referenced in memory. You can define your own interface into any external persistence type, through the optional plugin function. For example, Web Storage API's Storage interface, for which a plugin is already defined.

It must return two methods - write and read. These provide the transactional semantics between the defined store and the consumer application that invokes the mutations.

AtomInstance API


Returns the current atom value.

.write(fn(currentValue) {}, ...context)

Replaces the current atom value with the return value of the fn invocation. You may also optionally provide any number of context arguments, which will be appended to .watch invocations.

  • fn: A function whose return value is the new value of the store. The provided argument to fn is the current atom value (currentValue). You can pass any additional arguments to fn by binding them. For example, fn.bind(null, firstArg, secondArg)

.watch(fn(nextValue, prevValue, ...context) {})

Invokes the given function whenever the atom value changes. Also provides any context arguments that were handed off by the initiating .write call.

  • fn: A function that is invoked whenever the atom value changes.


🍔 A Clojure-inspired atom implementation in Javascript with configurability for external persistance







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