Template refs for DOM access in Vue - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a template ref in Vue?

A template ref is a way to directly access a DOM element or a component instance inside the Vue template using a special attribute called ref. It helps you interact with the element or component in your script.

beginner

How do you define a template ref on an element in Vue 3 Composition API?

You add <code>ref="name"</code> to the element in the template, then in the script use <code>const name = ref(null)</code> and Vue will link the DOM element to this variable after rendering.

intermediate

Why should you avoid manipulating the DOM directly in Vue?

Vue manages the DOM for you reactively. Direct DOM manipulation can cause conflicts or unexpected behavior. Template refs should be used carefully and mostly for things Vue can't handle, like focusing an input.

beginner

How do you access a DOM element using a template ref in Vue 3?

After defining a ref in the template and script, you access the DOM element with name.value. For example, inputRef.value.focus() sets focus on the input element.

intermediate

What is the difference between ref and reactive in Vue?

ref creates a reactive reference to a single value or DOM element, accessed with .value. reactive creates a reactive object with multiple properties. Template refs use ref for DOM access.

How do you declare a template ref for a DOM element in Vue 3 Composition API?

A Use <code>ref="name"</code> in template and <code>const name = ref(null)</code> in script

B Use <code>v-model="name"</code> in template and <code>const name = reactive({})</code> in script

C Use <code>id="name"</code> in template and <code>document.getElementById('name')</code> in script

D Use <code>ref="name"</code> in template and <code>const name = reactive(null)</code> in script

Template refs require the ref attribute in the template and a matching ref variable in the script initialized to null.

What is the correct way to access the DOM element from a template ref named inputRef?

A <code>inputRef.value</code>

B <code>inputRef</code>

C <code>inputRef.dom</code>

D <code>inputRef.element</code>

In Vue 3, refs are accessed with .value to get the actual DOM element or value.

When is it appropriate to use template refs in Vue?

A To replace all reactive data binding

B To declare global variables

C To style elements with CSS

D To directly manipulate DOM elements when Vue cannot handle it

Template refs are used for direct DOM access when needed, like focusing inputs, but not for general reactive data.

Which Vue API is used to create a reactive reference for template refs?

A computed()

B reactive()

C ref()

D watch()

ref() creates a reactive reference suitable for template refs.

What will happen if you try to access a template ref before the component is mounted?

A It will return the DOM element immediately

B It will be null or undefined

C It will throw a syntax error

D It will automatically mount the component

Template refs are only set after the component is mounted, so before that they are null.

Explain how to use template refs in Vue 3 to focus an input element after the component loads.

Think about linking template and script with ref, then using lifecycle to access DOM.

Describe the difference between using template refs and reactive data in Vue.

Consider when you want to change the UI vs when you want to reach the actual element.

Practice

1. What is the main purpose of using template refs in Vue?

easy

A. To directly access DOM elements or child components from the template

B. To define reactive state variables

C. To create computed properties

D. To register global components

Solution

1. Step 1: Understand what template refs do

   Template refs provide a way to directly access DOM elements or child components inside Vue templates.

2. Step 2: Compare with other Vue features

   Reactive state variables and computed properties are for data management, not direct DOM access. Global components registration is unrelated.

3. Final Answer:

   To directly access DOM elements or child components from the template -> Option A

4. Quick Check:

   Template refs = direct DOM/component access [OK]

Hint: Template refs connect template elements to script variables [OK]

Common Mistakes:

• Confusing refs with reactive state
• Thinking refs create computed properties
• Assuming refs register components

2. Which of the following is the correct way to declare a template ref in Vue 3's <script setup> syntax?

easy

A. const myRef = ref(null);

B. let myRef = reactive(null);

C. const myRef = computed(() => null);

D. var myRef = ref('element');

Solution

1. Step 1: Recall how to declare refs in Vue 3 script setup

   Use const myRef = ref(null); to create a ref variable initialized to null.

2. Step 2: Check other options for correctness

   reactive is for objects, not refs. computed is for derived values. Using var is discouraged and 'element' is not a valid initial value for a ref to DOM.

3. Final Answer:

   const myRef = ref(null); -> Option A

4. Quick Check:

   Declare ref with ref(null) [OK]

Hint: Use ref(null) to declare template refs in script setup [OK]

Common Mistakes:

• Using reactive instead of ref for DOM refs
• Initializing ref with wrong value
• Using var instead of const

3. Given the following Vue 3 component code, what will be logged when the button is clicked?

<template>
  <input ref="inputRef" />
  <button @click="focusInput">Focus</button>
</template>

<script setup>
import { ref } from 'vue';
const inputRef = ref(null);
function focusInput() {
  console.log(inputRef.value.tagName);
  inputRef.value.focus();
}
</script>

medium

A. undefined will be logged and an error occurs

B. "inputRef" will be logged and the input will get focus

C. "INPUT" will be logged and the input will get focus

D. Nothing will be logged and no focus happens

Solution

1. Step 1: Understand what inputRef.value refers to

   inputRef is a ref to the input DOM element, so inputRef.value is the actual input element.

2. Step 2: Check what tagName returns and focus behavior

   inputRef.value.tagName returns the uppercase tag name "INPUT". Calling focus() sets keyboard focus on the input.

3. Final Answer:

   "INPUT" will be logged and the input will get focus -> Option C

4. Quick Check:

   inputRef.value.tagName = "INPUT" and focus works [OK]

Hint: Ref value holds the DOM element; tagName is uppercase [OK]

Common Mistakes:

• Logging the ref variable name instead of its value
• Forgetting to use .value to access the element
• Assuming tagName is lowercase

4. Identify the error in this Vue 3 code snippet using template refs:

<template>
  <div ref="box">Content</div>
</template>

<script setup>
import { ref } from 'vue';
const box = ref();
console.log(box.value.textContent);
</script>

medium

A. The ref variable 'box' is not initialized with null

B. Accessing box.value.textContent before DOM is mounted causes error

C. The ref attribute should be used as :ref instead of ref

D. Missing import of onMounted to access DOM safely

Solution

1. Step 1: Check ref initialization and usage timing

   box is declared as ref() without initial value, which defaults to undefined. Accessing box.value.textContent immediately runs before DOM is ready.

2. Step 2: Understand Vue lifecycle for DOM refs

   Template refs are assigned after the component mounts. Accessing them too early (during setup) causes box.value to be null or undefined, so textContent access fails.

3. Final Answer:

   Accessing box.value.textContent before DOM is mounted causes error -> Option B

4. Quick Check:

   Access DOM refs only after mount [OK]

Hint: Access refs after mount, not immediately in setup [OK]

Common Mistakes:

• Trying to read ref value before DOM exists
• Not initializing ref with null (less critical)
• Confusing ref attribute syntax

5. You want to create a Vue 3 component that automatically focuses an input element when the component is mounted using template refs. Which code snippet correctly implements this behavior?

hard

A. <template>
<input :ref="inputRef" />
</template>

<script setup>
import { ref, onMounted } from 'vue';
const inputRef = ref(null);
onMounted(() => {
inputRef.focus();
});
</script>

B. <template>
<input ref="inputRef" />
</template>

<script setup>
import { ref } from 'vue';
const inputRef = ref(null);
inputRef.value.focus();
</script>

C. <template>
<input ref="inputRef" />
</template>

<script setup>
import { ref, onMounted } from 'vue';
const inputRef = ref(null);
onMounted(() => {
inputRef.value.focus();
});
inputRef.value.focus();
</script>

D. <template>
<input ref="inputRef" />
</template>

<script setup>
import { ref, onMounted } from 'vue';
const inputRef = ref(null);
onMounted(() => {
inputRef.value.focus();
});
</script>

Solution

1. Step 1: Use onMounted to run code after DOM is ready

   To safely access the input element, focus must be called inside onMounted lifecycle hook.

2. Step 2: Access the DOM element via inputRef.value and call focus()

   inputRef is a ref initialized to null, and inputRef.value holds the DOM element after mount. Calling inputRef.value.focus() sets focus correctly.

3. Final Answer:

   Code snippet C correctly uses onMounted and inputRef.value.focus() -> Option D

4. Quick Check:

   Use onMounted + inputRef.value.focus() [OK]

Hint: Focus input inside onMounted using inputRef.value.focus() [OK]

Common Mistakes:

• Calling focus outside onMounted before DOM ready
• Using :ref instead of ref attribute
• Calling focus on ref instead of ref.value