Detailed explanation of classnames function in Vue3: flexible class name rendering method

In Vue3, it is often necessary to dynamically generate class names in components. Such as transforming the style of an element in response to user interaction, or adding a class name to a specific item when rendering items in a list.

In such cases, the classnames function is a very useful tool, which can help us generate class names more conveniently and flexibly.

This article will introduce in detail the usage of the classnames function and how to use it in Vue3.

What is the classnames function?

The classnames function is a Javascript library that can combine multiple class name strings into a single class name string.

The following is a simple example:

import classNames from 'classnames';

const isActive = true;
const classNamesString = classNames('button', { 'is-active': isActive });
console.log(classNamesString); // "button is-active"

In the above code, we use the classnames function to convert the two class name strings 'button' and 'is-active' is merged into a class name string of 'button is-active'.

classNamesFunction accepts any number of parameters. In addition to the class name string, it can also receive an object as a parameter. This object contains several key-value pairs, where the key is a class name string and the value is a Boolean value. If a Boolean value is true, the corresponding class name will be included in the final output class name string. If the boolean value is false, the corresponding class name is ignored.

In the above example, we specify a class name named 'is-active' through the object { 'is-active': isActive } , its value is true. Therefore, when the isActive variable is true, the final class name string contains the class name 'is-active'.

The classnames function can also receive multiple parameters, each parameter can be a class name string or an object. In this way, we can combine multiple class name strings and objects to generate a complex class name string.

The following is a more complex example:

import classNames from 'classnames';

const size = 'small';
const color = 'blue';
const disabled = true;
const classNamesString = classNames(
  'button',
  { 'is-disabled': disabled },
  `${color}-background`,
  `${size}-text`
);
console.log(classNamesString); // "button is-disabled blue-background small-text"

In the above code, we specify a name through the object { 'is-disabled': disabled } It is the class name of 'is-disabled', and its value is true. Therefore, when the disabled variable is true, the final class name string contains the class name 'is-disabled'.

In addition to objects, we can also pass strings directly to the classnames function. In the above code, we pass the two strings with variables ${color}-background and ${size}-text to the classnames function, which will Include these strings as class name strings in the final output class name string.

How to use classnames function in Vue3?

In Vue3, using the classnames function is very simple. We only need to import the classnames function in the component and apply it to the elements that need to be rendered.

The following is an example component that uses the classnames function to generate class names for elements:

<template>
  <div
    :class="[
      'button',
      classNames({
        'is-active': isActive,
        'is-disabled': isDisabled
      })
    ]"
  >
    {{ text }}
  </div>
</template>

<script>
import { defineComponent } from 'vue';
import classNames from 'classnames';

export default defineComponent({
  props: {
    text: String,
    isActive: Boolean,
    isDisabled: Boolean
  },
  setup(props) {
    return {
      classNames
    };
  }
});
</script>

In the above code, we use Vue3's class binding to dynamically generate elements. Class name. We pass an array to :class, which contains the class name string 'button' and an expression that calls the classnames function.

When calling the classnames function, we pass an object containing two key-value pairs. The two keys are 'is-active' and 'is-disabled', and their values ​​are isActive and isDisabled respectively. These two component properties. When these properties are true, the corresponding class name will be included in the final output class name string.

The trick is to attach the classnames function to the component's setup() function and return it as a reactive object. In this way, this function can be directly referenced in the component's template.

Conclusion

The classnames function is a very useful Javascript library, which can help us generate class name strings more conveniently and flexibly. In Vue3, we can easily use the classnames function to dynamically render the class names of elements.

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