The defineModel macro solves the redundant code problem when custom components implement v-model in Vue 3.4. 1. It automatically creates modelValue prop and update:modelValue events in <script setup>. 2. Supports custom attribute names and event names through parameters, 3. It can pass options such as types and default values. 4. As a compile-time macro, eliminates runtime overhead, 5. Makes the two-way binding of parent-child components more concise and efficient, and ultimately achieves less code, the same behavior, and clearer intentions.
The defineModel macro in Vue 3.4 is a compiler macro that simplifies two-way binding (v-model) in custom components by automatically creating a modelValue prop and an update:modelValue event — or a custom prop/event pair — with minimal boilerplate.
It was introduced in Vue 3.4 as a syntax sugar to make writing v-model-compatible components much cleaner, especially in <script setup></script> .
? What problem does it solve?
Before defineModel , if you wanted to support v-model in a component, you had to manually define:
<script setup> defineProps(['modelValue']) defineEmits(['update:modelValue']) </script>
Then bind it in the template:
<input :value="modelValue" @input="$emit('update:modelValue', $event.target.value)" >
This is repetitive and verbose.
? How defineModel works
With defineModel , Vue automatically generates the prop and emit declaration:
<script setup> const modelValue = defineModel() </script> <template> <input v-model="modelValue"> </template>
This single line replaces both the prop and emit definition.
Under the hood, it's equivalent to:
defineProps(['modelValue']) defineEmits(['update:modelValue'])
But now you can directly read and write modelValue like a ref.
? Customizing the model
You can also use a custom prop name and event using arguments:
<script setup>
const checked = defineModel('checked', { type: Boolean })
</script>
<template>
<input type="checkbox" v-model="checked">
</template>This creates:
- A prop named
checked - An event named
update:checked
You can even pass options like type , required , etc., just like with defineProps .
const count = defineModel('count', {
type: Number,
default: 0
})?? Important Notes
-
defineModelis only available inside<script setup>. - It's a compiler macro , so it doesn't exist at runtime. It gets compiled away during build.
- It only works in SFCs (Single File Components) with build tool support (eg, Vite, Vue CLI).
- Not available in plain JavaScript or runtime-rendered components.
? Two-way binding made easy
Now parent usage stays the same:
<ChildComponent v-model="searchText" />
And the child handles it with zero boilerplate.
Summary
defineModel in Vue 3.4:
- Reduces boilerplate for
v-modelsupport - Acts as a ref-like value that syncs with the parent
- Supports custom names and type options
- Is a compile-time helper (no runtime cost)
It's a small but powerful quality-of-life improvement for component authors.
Basically: less code, same behavior, cleaner intent.
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