Why must composables be called synchronously in rather than in a callback? onMounted(() => { const { x } = useMouse(); // problem });

Vue needs the active component instance to register the composable's lifecycle hooks and watchers

Composables can only be called once per app

Callbacks run on the server only

Vue · Middle · Question 23 of 75

Why must composables be called synchronously in `<script setup>` rather than in a callback?

onMounted(() => {
  const { x } = useMouse(); // problem
});

✓Correct answer: Vue needs the active component instance to register the composable's lifecycle hooks and watchers
2Composables can only be called once per app
3Callbacks run on the server only

Explanation

Inside a callback there is no current instance, so onUnmounted inside the composable isn't registered and listeners leak. <script setup> restores the instance after a top-level await, so calls after it still work.

Why must composables be called synchronously in `<script setup>` rather than in a callback?

Explanation

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Why must composables be called synchronously in <script setup> rather than in a callback?

Explanation

Further reading

Test yourself

Why must composables be called synchronously in `<script setup>` rather than in a callback?