How to determine when Vue has finished updating the DOM?

If vue does not have a callback for this you can use a MutationObserver listener on the parent: https://developer.mozilla.org/en/docs/Web/API/MutationObserver

Vue batches DOM updates and performs them asynchronously for performance reasons. After a data change, you can use Vue.nextTick to wait for the DOM updates to finish:

subtasks.push({});
Vue.nextTick(function () {
  // DOM updated
});

If you are using it inside a component method where this is available (and a reference to the component), you can use:

this.$nextTick(function () {
  // DOM updated
});

References:

Vue.nextTick

vm.$nextTick