How to use v-show and v-if to render different types of data in Vue

Vue is one of the most popular front-end frameworks today. It adopts the MVVM architectural pattern and makes front-end development more efficient and simpler through data-driven views. In Vue, v-show and v-if are commonly used instructions. They can control the display or rendering of DOM elements.

However, during the development process, we often need to use different DOM structures to render according to different types of data. At this time, the difference between v-show and v-if is particularly important.

First of all, v-show is an instruction to control the style of DOM elements. It controls the visibility of elements through the display attribute of CSS. When the expression bound to v-show is true, the element will be displayed, otherwise it will be hidden. Here's an example:

<div v-show="isShow">这里是要显示的内容</div>

In this example, we bind the Boolean value isShow through v-show. When isShow is true, the div element will be displayed. If isShow is false, the element is hidden, but it still exists in the DOM.

In contrast, v-if is an instruction that controls the presence or absence of DOM elements. When the expression bound by v-if is true, the element will be rendered into the DOM, otherwise it will not be rendered. Here's an example:

<div v-if="isRender">这里是要渲染的内容</div>

In this example, we bind the Boolean value isRender through v-if. When isRender is true, the div element will be rendered into the DOM. If isRender is false, the element will not be rendered into the DOM.

To sum up, v-show controls the display and hiding of elements. It is only realized through the display attribute of CSS and is completed by modifying existing DOM elements. v-if controls the presence or absence of elements. It is implemented by dynamically manipulating the DOM and frequently performs insertion or deletion operations.

So how to choose between v-show or v-if according to different types of data? Here's an example:

<div>
  <ul v-show="isShowList">
    <li v-for="item in list">{{item.name}}</li>
  </ul>
  <table v-if="isShowTable">
    <thead>
      <tr>
        <th>Name</th>
        <th>Age</th>
      </tr>
    </thead>
    <tbody>
      <tr v-for="item in list">
        <td>{{item.name}}</td>
        <td>{{item.age}}</td>
      </tr>
    </tbody>
  </table>
</div>

In this example, we use v-show to control the display and hiding of a ul list, and use v-if to control the rendering of a table. When isShowList is true, the ul list will be displayed; when isShowTable is true, the table table will be rendered.

Through the above example, we can find that when you need to dynamically display or hide an existing DOM element, v-show should be used. When you need to dynamically generate different DOM elements based on different types of data, you should use v-if.

Of course, in actual development, we do not only have to choose one instruction to display data. We can use v-show and v-if in combination to complete the requirements for different types of data display. It should be noted that when the amount of data is large, dynamically inserting or deleting DOM elements will bring greater performance pressure to the page. Therefore, we should try to avoid frequent insertion or deletion operations and try to use v-show to control existing DOM elements.

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