TransitionGroup #

<TransitionGroup> is a built-in component designed for animating the insertion, removal, and order change of elements or components that are rendered in a list.

Differences from <Transition> #

<TransitionGroup> supports the same props, CSS transition classes, and JavaScript hook listeners as <Transition>, with the following differences:

• By default, it doesn't render a wrapper element. But you can specify an element to be rendered with the tag prop.

• Transition modes are not available, because we are no longer alternating between mutually exclusive elements.

• Elements inside are always required to have a unique key attribute.

• CSS transition classes will be applied to individual elements in the list, not to the group / container itself.

Enter / Leave Transitions #

Here is an example of applying enter / leave transitions to a v-for list using <TransitionGroup>:

<TransitionGroup name="list" tag="ul">
  <li v-for="item in items" :key="item">
    {{ item }}
  </li>
</TransitionGroup>

.list-enter-active,
.list-leave-active {
  transition: all 0.5s ease;
}
.list-enter-from,
.list-leave-to {
  opacity: 0;
  transform: translateX(30px);
}

Move Transitions #

The above demo has some obvious flaws: when an item is inserted or removed, its surrounding items instantly "jump" into place instead of moving smoothly. We can fix this by adding a few additional CSS rules:

.list-move, /* apply transition to moving elements */
.list-enter-active,
.list-leave-active {
  transition: all 0.5s ease;
}

.list-enter-from,
.list-leave-to {
  opacity: 0;
  transform: translateX(30px);
}

/* ensure leaving items are taken out of layout flow so that moving
   animations can be calculated correctly. */
.list-leave-active {
  position: absolute;
}

Now it looks much better - even animating smoothly when the whole list is shuffled:

Full Example

Staggering List Transitions #

By communicating with JavaScript transitions through data attributes, it's also possible to stagger transitions in a list. First, we render the index of an item as a data attribute on the DOM element:

<TransitionGroup
  tag="ul"
  :css="false"
  @before-enter="onBeforeEnter"
  @enter="onEnter"
  @leave="onLeave"
>
  <li
    v-for="(item, index) in computedList"
    :key="item.msg"
    :data-index="index"
  >
    {{ item.msg }}
  </li>
</TransitionGroup>

Then, in JavaScript hooks, we animate the element with a delay based on the data attribute. This example is using the GreenSock library to perform the animation:

function onEnter(el, done) {
  gsap.to(el, {
    opacity: 1,
    height: '1.6em',
    delay: el.dataset.index * 0.15,
    onComplete: done
  })
}

Related

• <TransitionGroup> API reference