code: function getSubscribableForArray(ko, array) {
    var subscribable = array._subscribable;
    var signal = {};
  
    if (!subscribable) {
      subscribable = array._subscribable = new ko.subscribable();
  
      wrapStandardArrayMutators(array, subscribable, signal);
      addKnockoutArrayMutators(ko, array, subscribable, signal);
    }
  
    return subscribable;
  }
docs: Gets or creates a subscribable that fires after each array mutation