Use js to modify css in vue

Preface

Vue.js is a popular JavaScript framework. Its lightweight MVVM framework and many tools make it the first choice for front-end engineers. In the Vue.js framework, we often need to modify CSS styles in JavaScript code. This is also the topic discussed in this article.

Using JS to modify CSS in Vue

In Vue.js, we can easily bind CSS styles to achieve dynamic changes in styles. But in some scenarios, we may need to modify CSS styles through JavaScript code. At this time, we need to use some tools and methods provided by Vue.js.

1. Get elements through $refs

In Vue.js, we can use $refs to get DOM elements and modify the CSS style of the element through JavaScript. For example, the following code demonstrates how to obtain a DOM element through $refs and modify the background color of the element:

HTML:

<div ref="mydiv">这是一个DIV元素</div>

JavaScript:

<script>
export default {
  mounted(){
    this.$refs.mydiv.style.backgroundColor = 'red'
  }
}
</script>

The above code , we use this.$refs in the mounted hook function to obtain the DOM element with the ID "mydiv" and modify the background color of the element.

It should be noted that $refs can only be used in the mounted function, because the DOM element will be correctly rendered only after the function is executed.

2. Using vue-style-loader

Vue.js provides a very convenient tool vue-style-loader, which can dynamically insert style sheets into the DOM middle. We can use the following code to install vue-style-loader:

npm install vue-style-loader --save-dev

The usage is as follows:

JavaScript:

<style>
  .myclass {
    background-color:red;
  }
</style>

<script>
import 'vue-style-loader'

export default {
  mounted(){
    const style = document.createElement('style')
    style.innerText = `
      .myclass {
        background-color: yellow;
      }
    `
    document.head.appendChild(style)
  }
}
</script>

In the above code, we use vue-style-loader The style sheet is dynamically inserted into the DOM. We can also use JavaScript to dynamically modify the CSS styles in this style sheet.

3. Using computed properties

In Vue.js, we can return CSS style objects through computed properties, so that we can bind them directly in the Vue template CSS styles are more convenient to use. For example, the following code demonstrates how to use calculated properties to return CSS styles:

JavaScript:

<script>
export default {
  data(){
    return {
        bgColor: 'red'
    }
  },
  computed:{
    myStyle(){
      return {
        backgroundColor: this.bgColor
      }
    }
  }
}
</script>

<template>
  <div :style="myStyle">这是一个DIV元素</div>
</template>

In the above code, we return a CSS style object through the calculated property myStyle, which contains element's backgroundColor property.

Conclusion

This article introduces how to use JavaScript to modify CSS styles in the Vue.js framework. We can get DOM elements and modify their CSS styles through $refs, dynamically insert style sheets using vue-style-loader, or use computed properties to return CSS style objects. If you encounter problems when developing a Vue.js project, I believe these tips can help you solve the problem.

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