Understanding Deep Selectors in Vue.js Scoped CSS
Understanding Deep Selectors in Vue.js Scoped CSS
When developing applications with Vue.js, you often use scoped CSS to ensure that your styles are confined to specific components. While this encapsulation is beneficial for maintaining clean styles, there are situations when you want to target nested components that are not directly styled due to the scoped nature. This is where deep selectors come into play.
The Problem with Scoped CSS
Scoped CSS (using <style scoped>) restricts your styles to the component they are defined in. This means that styles won’t “leak” out to other components, preserving the design integrity. However, there are cases, especially when working with third-party component libraries like Vuetify, where you want to style child components or elements deeply nested within your component.
The Solution: Deep Selectors
To handle this, Vue.js provides several “deep selectors” that allow you to penetrate the scope and apply styles to nested components:
>>>- The legacy deep selector for scoped CSS, compatible with webpack/vue-cli.::v-deep- The recommended deep selector in Vue 3, ensuring future compatibility./deep/- Another deprecated version that is still recognized by tools like SASS and PostCSS.
Understanding the Selectors
| Selector | Description |
|---|---|
>>> |
Former deep selector for scoped CSS (webpack/vue-cli compatible). |
/deep/ |
Similar to >>> but written differently; less recommended. |
::v-deep |
Officially recommended syntax starting from Vue 3 and Vite. |
All three selectors serve the same purpose: they break through the component’s style encapsulation.
Example Usage
Let’s consider an example where you want to style a button from Vuetify within your Vue component.
Code Sample
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<template>
<v-btn class="my-btn">Click Me</v-btn>
</template>
<style scoped>
.my-btn >>> .v-btn__content {
color: red;
}
</style>
Or using the modern syntax:
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<style scoped>
.my-btn ::v-deep .v-btn__content {
color: red;
}
</style>
In the above examples, without a deep selector, the styles would not apply to .v-btn__content because it resides within a child component. By using ::v-deep or >>>, we can effectively style it.
Visualizing the Difference
Consider the following comparisons illustrating which styles work and which do not with and without deep selectors:
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<style scoped>
/* ❌ Does NOT work without a deep selector */
.my-btn .v-btn__content {
color: red;
}
/* ✅ Works with a deep selector */
.my-btn ::v-deep .v-btn__content {
color: red;
}
</style>
Working with Vite and Vue 3
If you are using Vite along with Vue 3, you can simplify your syntax even further:
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<style scoped>
.my-class ::v-deep(.child-class) {
/* styles for deep children */
}
/* Even more concise */
::v-deep(.child-class) {
/* global access */
}
</style>
Conclusion
Deep selectors are essential tools when working with scoped CSS in Vue.js, enabling you to effectively apply styles to nested components. When your styles seem ineffective due to scoped limitations, remember that selectors like ::v-deep or >>> can help you reach those deep child elements.
Understanding and utilizing deep selectors ensures that your components not only look good but are also styled precisely as you intend them to be, even when using third-party libraries.