Essential skills for beginners to learn Vue: master v-if, v-show, v-else, v-else-if conditional rendering

Essential skills for beginners to Vue: Master v-if, v-show, v-else, v-else-if conditional rendering, specific code examples are required

Introduction:
Vue.js is a popular front-end JavaScript framework that provides powerful tools and features to build interactive user interfaces. In Vue, v-if, v-show, v-else and v-else-if are commonly used conditional rendering instructions that help show or hide elements based on specific conditions. In this article, we will introduce the use of these instructions and help beginners understand and master these skills through specific code examples.

1. v-if instruction
The v-if instruction is one of the most commonly used conditional rendering instructions in Vue. It determines whether to render an element based on the value of a given expression. If the expression evaluates to true, the element will be rendered; if it evaluates to false, the element will be removed.

The following is a simple example showing the usage of the v-if directive:

<template>
  <div>
    <p v-if="isShow">这是一个v-if指令的示例</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isShow: true
    }
  }
}
</script>

In the above code, we define an isShow attribute in data and set its initial value Set to true. In the template, we use the v-if directive to determine whether to display the <p></p> element. Since the value of isShow is true, the element will be rendered.

2. v-show instruction
The v-show instruction is similar to the v-if instruction. It also determines whether the element is displayed based on the value of the given expression. The difference is that the v-show instruction retains the DOM structure of the element and only controls the display and hiding of the element through CSS styles.

The following is a simple example showing the usage of the v-show directive:

<template>
  <div>
    <p v-show="isShow">这是一个v-show指令的示例</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isShow: true
    }
  }
}
</script>

In the above code, we define an isShow attribute in data and set its initial value Set to true. In the template, we use the v-show directive to decide whether to display the <p></p> element. Since the value of isShow is true, the element will be displayed.

3. v-else instruction
The v-else instruction is used to add an "else" conditional block after the previous element with v-if or v-else-if. It has no expression and can only be used in v-else to indicate that the element will be rendered when the previous conditions are not met.

The following is a simple example demonstrating the use of the v-else directive:

<template>
  <div>
    <p v-if="isShow">这是一个v-if指令的示例</p>
    <p v-else>这是一个v-else指令的示例</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isShow: false
    }
  }
}
</script>

In the above code, we decide which one to display based on the value of isShow

element. Since the value of isShow is false, the v-if condition is not met, and the <p></p> element after the v-else directive will be displayed.

4. v-else-if instruction
The v-else-if instruction is used to add an "else if" conditional block after the v-if or v-else-if instruction. It receives an expression and determines whether to render the element based on the value of the expression.

The following is a simple example that demonstrates the use of the v-else-if directive:

<template>
  <div>
    <p v-if="type === 'info'">这是一个信息提示</p>
    <p v-else-if="type === 'warning'">这是一个警告提示</p>
    <p v-else-if="type === 'error'">这是一个错误提示</p>
    <p v-else>这是一个未知提示</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      type: 'warning'
    }
  }
}
</script>

In the above code, we determine which one to display based on the value of type&lt ;p> element. Since the value of type is 'warning', the condition in the v-else-if directive is met, and the <p></p> element "This is a warning prompt" will be displayed.

Summary:
v-if, v-show, v-else and v-else-if are commonly used conditional rendering instructions in Vue, through which we can dynamically show or hide elements. In some specific scenarios, we can choose which instruction to use based on conditions. Mastering these instructions is very important for developers who are new to Vue. Through the specific code examples in this article, beginners can understand and apply these instructions more clearly, thereby improving their Vue development capabilities.

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