Inline Manual Player: unlimited undo

unlimited_undo.js

// take latest step from the list of previous steps and activate it
function activatePreviousStep () {
  var steps_history = JSON.parse(localStorage.getItem('inm_steps_history')) || [];
  var step_data = steps_history.pop();
  if (step_data) {
    inline_manual_player.activateStep(step_data.topic_id, step_data.step_index);
  }
  localStorage.setItem('inm_steps_history', JSON.stringify(steps_history));
}

// whenever step is deactivated, add it to the list of previous steps
inline_manual_player.setOptions({
  callbacks: {
    onStepDeactivate: function (player, topic_id, step_index) {
      var steps_history = JSON.parse(localStorage.getItem('inm_steps_history')) || [];
      steps_history.push({
        topic_id: topic_id,
        step_index: step_index
      });
      // cap steps history to 100 items, to prevent storage size overflow
      steps_history = steps_history.slice(-100);
      localStorage.setItem('inm_steps_history', JSON.stringify(steps_history));
    }
  }
});