Vue Conditional Rendering Guide: Technical Analysis of v-if, v-show, v-else, v-else-if

Vue is a popular JavaScript framework that provides a simple and easy-to-use syntax to implement conditional rendering. Conditional rendering refers to showing or hiding specific elements or components based on certain conditions so that different content can be displayed according to different situations.

In Vue, we can use four instructions to implement conditional rendering, which are v-if, v-show, v-else, and v-else-if. Below we will provide a detailed technical analysis of them and provide specific code examples.

1. v-if directive: v-if is the most common and commonly used conditional rendering directive. It determines whether to render a specific element or component based on the value of a given expression.

   <div v-if="isVisible">
   <!-- 渲染的内容 -->
   </div>

   In the above example, when the value of isVisible is true, the content in the div element is rendered; when the value of isVisible is false, the content is not rendered. the div.

2. v-show directive: The v-show directive is also used for conditional rendering. It is different from v-if in that the element will always be rendered regardless of whether the condition is met, but it can be based on Conditions to control the display and hiding of elements.

   <div v-show="isVisible">
   <!-- 渲染的内容 -->
   </div>

   In the above example, when the value of isVisible is true, the element is displayed; when the value of isVisible is false, the element is hidden.

3. v-else directive: The v-else directive is used to render another element after the v-if directive. It must immediately follow the v-if or v-else-if directive and does not require any conditions to trigger.

   <div v-if="isTrue">
   <!-- 渲染的内容 -->
   </div>
   <div v-else>
   <!-- 另一个渲染的内容 -->
   </div>

   In the above example, if the value of isTrue is true, the content in the first div is rendered; if the value of isTrue is false, then Render the content in the second div.

4. v-else-if directive: The v-else-if directive is used to render another conditional element after the v-if directive. It can be used for multiple consecutive conditions. render.

   <div v-if="condition1">
   <!-- 渲染的内容 -->
   </div>
   <div v-else-if="condition2">
   <!-- 渲染的内容 -->
   </div>
   <div v-else>
   <!-- 渲染的内容 -->
   </div>

   In the above example, if the value of condition1 is true, the content in the first div is rendered; if the value of condition1 is false, and If the value of condition2 is true, the content in the second div will be rendered; if the values ​​of condition1 and condition2 are both false, the third div will be rendered. content in.

It should be noted that v-if has a higher switching overhead, while v-show has a higher initial rendering overhead. Therefore, if you need to frequently switch between showing and hiding, you can use the v-show instruction; if you need to hide an element when runtime conditions are not met, you can use the v-if instruction.

To summarize, Vue's conditional rendering provides a variety of instructions to flexibly render specific elements or components based on different conditions. We can choose to use v-if, v-show, v-else, v-else-if and other instructions according to actual needs to flexibly control the display and hiding of pages. By using these instructions appropriately, we can easily implement condition-based dynamic rendering and improve the interactivity and user experience of web pages.

I hope the above technical analysis will be helpful to you. You are welcome to try and use these conditional rendering instructions in actual projects. I wish you success in Vue development!

The above is the detailed content of Vue Conditional Rendering Guide: Technical Analysis of v-if, v-show, v-else, v-else-if. For more information, please follow other related articles on the PHP Chinese website!