chore: init monorepo with existing website and plans

2026-06-15 02:31:15 +08:00
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+---
+title: Teleport Target Must Exist Before Mount
+impact: HIGH
+impactDescription: Teleport will fail silently or throw errors if target element doesn't exist when component mounts
+type: gotcha
+tags: [vue3, teleport, modal, dom, lifecycle]
+---
+
+# Teleport Target Must Exist Before Mount
+
+**Impact: HIGH** - The teleport `to` target must already exist in the DOM when the `<Teleport>` component is mounted. If the target doesn't exist, Vue will throw an error and the teleported content won't render.
+
+This is a common source of bugs when using modals, tooltips, or other teleported UI elements, especially when targeting Vue-rendered elements.
+
+## Task Checklist
+
+- [ ] Ensure teleport target exists in the DOM before `<Teleport>` mounts
+- [ ] Place teleport containers (e.g., `#modals`, `#tooltips`) in `index.html` outside the Vue app
+- [ ] If targeting Vue-rendered elements, ensure they mount before the Teleport
+- [ ] Use Vue 3.5+ `defer` prop when target is rendered later in the same component tree
+
+**Incorrect:**
+```vue
+<template>
+  <!-- ERROR: Target doesn't exist yet when Teleport mounts -->
+  <Teleport to="#modal-container">
+    <div class="modal">Modal content</div>
+  </Teleport>
+
+  <!-- Target is defined after the Teleport -->
+  <div id="modal-container"></div>
+</template>
+```
+
+**Correct - Option 1: External container in index.html:**
+```html
+<!-- index.html -->
+<body>
+  <div id="app"></div>
+  <!-- Container exists before Vue app mounts -->
+  <div id="modals"></div>
+  <div id="tooltips"></div>
+</body>
+```
+
+```vue
+<template>
+  <!-- Safe: #modals exists before any Vue component mounts -->
+  <Teleport to="#modals">
+    <div v-if="showModal" class="modal">Modal content</div>
+  </Teleport>
+</template>
+```
+
+**Correct - Option 2: Teleport to body:**
+```vue
+<template>
+  <!-- Safe: body always exists -->
+  <Teleport to="body">
+    <div v-if="showModal" class="modal">Modal content</div>
+  </Teleport>
+</template>
+```
+
+**Correct - Option 3: Vue 3.5+ defer prop:**
+```vue
+<template>
+  <!-- Works in Vue 3.5+: defer resolves target after other parts mount -->
+  <Teleport defer to="#late-container">
+    <div class="modal">Modal content</div>
+  </Teleport>
+
+  <!-- Target rendered later in template -->
+  <div id="late-container"></div>
+</template>
+```
+
+## Defer Prop Limitations (Vue 3.5+)
+
+The `defer` prop only waits for elements rendered in the **same mount/update tick**:
+
+```vue
+<template>
+  <!-- ERROR: defer won't help if target mounts asynchronously -->
+  <Teleport defer to="#async-container">
+    <div>Content</div>
+  </Teleport>
+
+  <!-- If this component loads asynchronously, defer won't work -->
+  <Suspense>
+    <AsyncComponent />  <!-- Contains #async-container -->
+  </Suspense>
+</template>
+```
+
+## Common Patterns
+
+### Recommended: Centralized Teleport Containers
+```html
+<!-- index.html -->
+<body>
+  <div id="app"></div>
+
+  <!-- Teleport destinations outside Vue app -->
+  <div id="modals" aria-live="polite"></div>
+  <div id="notifications" aria-live="assertive"></div>
+  <div id="tooltips"></div>
+</body>
+```
+
+## Reference
+- [Vue.js Teleport - Using with Vue-rendered Targets](https://vuejs.org/guide/built-ins/teleport.html#using-with-vue-rendered-targets)
+- [Vue.js Teleport - Deferred Teleport](https://vuejs.org/guide/built-ins/teleport.html#deferred-teleport)