a function returning in graphviz dot language the state machine from https://github.com/nickuraltsev/finity

printMachine.js

const printMachine = stateMachineConfig => {
  // decorate=true -> as attribute is also useful, but colors are far better
  const edgeTimerAttributes = ', color="darkgreen", fontcolor="darkgreen"'
  const edgeSuccessAttributes = ', color="blue", fontcolor="blue"'
  const edgeFailAttributes = ', color="red", fontcolor="red"'
  let result = 'digraph {\n'
  result += Object.getOwnPropertyNames(stateMachineConfig.states).reduce((acc, stateName) => {
    let res = `${acc}`

    const stateObject = stateMachineConfig.states[stateName]
    const { timers, asyncActions } = stateObject // TODO events when I need them ...

    res += timers.reduce(
      (a, tim) => `${a}  ${stateName} -> ${tim.transitions[0].targetState} [label=" timeout: ${tim.timeout} ms"${edgeTimerAttributes}]\n`,
      ''
    )

    res += asyncActions.reduce((a, asyncAct) => {
      let r = `${a}`
      const successState = asyncAct.successTrigger.transitions[0].targetState
      const failureState = asyncAct.failureTrigger.transitions[0] ? asyncAct.failureTrigger.transitions[0].targetState : null
      if (successState) {
        r += `  ${stateName} -> ${successState} [label="${asyncAct.action.toString()} SUCCESS"${edgeSuccessAttributes}]\n`
      }
      if (failureState) {
        r += `  ${stateName} -> ${failureState} [label="${asyncAct.action.toString()} FAILURE"${edgeFailAttributes}]\n`
      }
      return r
    }, '')

    return res
  }, '')
  result += '}'
  return result
}