Tips for stopping Vue.js automatic merging of CSS classes

Question

Tips for stopping Vue.js automatic merging of CSS classes

Recently, I embarked on my journey with Vue.js and have been thoroughly enjoying the experience. However, I've stumbled upon a challenge that has me stumped. Despite searching high and low and studying the documentation, I haven't found a solution.

Vue.js has this nifty feature where it automatically adds or merges CSS classes to the root element of your child components when you apply a class. While this is handy, I need to disable this functionality for a specific component so that the classes are added to a child element of the root instead.

To better explain my predicament, I created a fiddle which can be viewed here.

<div id="demo">
  <child-component class="some-class"></child-component>
</div>

(The "some-class" is automatically applied, resulting in a green background color)

I'm now left wondering - how do I stop Vue.js from merging CSS classes automatically?

javascript vue.js vuejs2

Answer 1

Answer №1

In my opinion, a simpler approach would be to link the incoming class attribute and dynamic class property to the data, then remove them from the virtual node during the `created()` lifecycle hook.

Vue.component('child-component', {
  template: `
    <div class="child">
      <h1 :class="staticClass">Hello</h1>
    </div>
  `,
  
  data() {
    return {
      staticClass: [],
    }
  },

  created() {
    // dynamic :class prop
    this.staticClass.push(this.$vnode.data.class)
    // delete if not required on this.$el
    delete this.$vnode.data.class
    
    // static class attr
    this.staticClass.push(this.$vnode.data.staticClass)
    // delete if not necessary for this.$el
    delete this.$vnode.data.staticClass
  },
});

var demo = new Vue({
  el: '#demo',

  data: {
    dynamicClass: 'dynamic-class'
  },
});

.child {
  border: 1px solid red;
  padding: 20px;
  text-align: center;
}

.some-class {
  background-color: green;
}

.dynamic-class {
  border: 1px solid yellow;
}

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="7d0e0d1d38761128280b16293336">[email protected]</a>/dist/vue.min.js"></script>

<div id="demo">
  <child-component :class="dynamicClass" class="some-class"></child-component>
</div>

Answer 2

In my opinion, a simpler approach would be to link the incoming class attribute and dynamic class property to the data, then remove them from the virtual node during the `created()` lifecycle hook.

Vue.component('child-component', {
  template: `
    <div class="child">
      <h1 :class="staticClass">Hello</h1>
    </div>
  `,
  
  data() {
    return {
      staticClass: [],
    }
  },

  created() {
    // dynamic :class prop
    this.staticClass.push(this.$vnode.data.class)
    // delete if not required on this.$el
    delete this.$vnode.data.class
    
    // static class attr
    this.staticClass.push(this.$vnode.data.staticClass)
    // delete if not necessary for this.$el
    delete this.$vnode.data.staticClass
  },
});

var demo = new Vue({
  el: '#demo',

  data: {
    dynamicClass: 'dynamic-class'
  },
});

.child {
  border: 1px solid red;
  padding: 20px;
  text-align: center;
}

.some-class {
  background-color: green;
}

.dynamic-class {
  border: 1px solid yellow;
}

<script src="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="7d0e0d1d38761128280b16293336">[email protected]</a>/dist/vue.min.js"></script>

<div id="demo">
  <child-component :class="dynamicClass" class="some-class"></child-component>
</div>

Answer 3

Answer №2

Updated I have a different perspective on the intuitive nature of moving a class applied to a component to an inner element. In my opinion, it is not ideal and I recommend passing it as a prop instead.

Nevertheless, it is possible to achieve what you desire with some limitations. The component will possess a list of classes that are meant for the outer element. Upon being mounted, it checks $el.classList and identifies the classes that do not match those designated for the outer element. These unmatched classes are then transferred to the inner element and removed from the outer one. It is important to note that if any of the classes assigned to the outer element are also applied to the component, they will not be moved to the inner element. Furthermore, any changes made to the applied classes will not be detected.

Vue.component('child-component', {
  template: `<div :class="outerClasses"><h1 :class="childClasses">Hello</h1></div>`,
  data() {
    return {
      outerClasses: ['child'],
      childClasses: []
    };
  },
  mounted() {
    this.childClasses = Array.from(this.$el.classList).filter((c) => !this.outerClasses.includes(c));
    for (const c of this.childClasses) this.$el.classList.remove(c);
  }
});

var demo = new Vue({
  el: '#demo'
});

.child {
  border: 1px solid red;
  padding: 20px;
  text-align: center;
}

.some-class {
  background-color: green;
}

<script src="//vuejs.org/js/vue.min.js"></script>
<div id="demo">
  <child-component class="some-class a b c"></child-component>
</div>

Answer 4

Updated I have a different perspective on the intuitive nature of moving a class applied to a component to an inner element. In my opinion, it is not ideal and I recommend passing it as a prop instead.

Nevertheless, it is possible to achieve what you desire with some limitations. The component will possess a list of classes that are meant for the outer element. Upon being mounted, it checks $el.classList and identifies the classes that do not match those designated for the outer element. These unmatched classes are then transferred to the inner element and removed from the outer one. It is important to note that if any of the classes assigned to the outer element are also applied to the component, they will not be moved to the inner element. Furthermore, any changes made to the applied classes will not be detected.

Vue.component('child-component', {
  template: `<div :class="outerClasses"><h1 :class="childClasses">Hello</h1></div>`,
  data() {
    return {
      outerClasses: ['child'],
      childClasses: []
    };
  },
  mounted() {
    this.childClasses = Array.from(this.$el.classList).filter((c) => !this.outerClasses.includes(c));
    for (const c of this.childClasses) this.$el.classList.remove(c);
  }
});

var demo = new Vue({
  el: '#demo'
});

.child {
  border: 1px solid red;
  padding: 20px;
  text-align: center;
}

.some-class {
  background-color: green;
}

<script src="//vuejs.org/js/vue.min.js"></script>
<div id="demo">
  <child-component class="some-class a b c"></child-component>
</div>

Answer 5

Answer №3

To ensure that the style is correctly applied in Vue, it's recommended to wrap the entire content within an additional <div></div>. If you only want to style the <h1> element, you can achieve this with the following code:

template: `<div><h1 class="child">Hello</h1></div>`

By implementing this approach, you should see the desired outcome. Feel free to reach out if you encounter any issues.

Answer 6

To ensure that the style is correctly applied in Vue, it's recommended to wrap the entire content within an additional <div></div>. If you only want to style the <h1> element, you can achieve this with the following code:

template: `<div><h1 class="child">Hello</h1></div>`

By implementing this approach, you should see the desired outcome. Feel free to reach out if you encounter any issues.

Answer 7

Answer №4

It's important to recognize the presence of the wrapper div in your template and not try to abstract it away. Ignoring the existence of this div can lead to confusion and styling issues.

For example, if you successfully apply a class to a nested element within your component's template, it may appear as though the component consists only of that element without the surrounding div. While certain styles like background color will work as expected, layout-related styles such as position: absolute may not behave as intended due to the hierarchy of elements.

Users of the component should be aware of the structure of the template so they can style it appropriately, considering the presence of the wrapper div. It's worth noting that methods like using web components or the shadow DOM may allow for abstraction of the wrapper div, but these are beyond the scope of Vue.

Answer 8

It's important to recognize the presence of the wrapper div in your template and not try to abstract it away. Ignoring the existence of this div can lead to confusion and styling issues.

For example, if you successfully apply a class to a nested element within your component's template, it may appear as though the component consists only of that element without the surrounding div. While certain styles like background color will work as expected, layout-related styles such as position: absolute may not behave as intended due to the hierarchy of elements.

Users of the component should be aware of the structure of the template so they can style it appropriately, considering the presence of the wrapper div. It's worth noting that methods like using web components or the shadow DOM may allow for abstraction of the wrapper div, but these are beyond the scope of Vue.

Tips for stopping Vue.js automatic merging of CSS classes

Answer №1

Answer №2

Answer №3

Answer №4

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