How to use v-for in vue

v-for directive is used to iterate over an array or object and render a child component or template for each element. Its syntax is

, where item is an alias for each element and items is the array or object to be iterated over. v-for can render lists, tables and other structures. In order to track child components when elements are updated or rearranged, each child component needs to be assigned a unique key. Range variables such as index, $index, first, last, even and odd can be accessed in the v-for loop, but range variables can only be used in templates, not in JavaScript

Usage of v-for

v-for is a basic instruction in Vue.js, used to traverse an array or object and render a child component for each element or template.

Syntax:

<code class="javascript"><div v-for="item in items">
  <!-- 模板内容 -->
</div></code>

Parameters:

• item: Each item in the loop Alias ​​of element
• items:Array or object to be traversed

Usage:

v-for OK Used to render structures such as lists and tables. For example:

<code class="javascript"><ul>
  <li v-for="item in items">{{ item }}</li>
</ul></code>

This code will generate an unordered list containing each element in the items array.

Using Keys:

When rendering a list, it is important to specify a unique key for each child component so that Vue.js can track when elements are updated or rearranged they.

<code class="javascript"><ul>
  <li v-for="item in items" :key="item.id">{{ item.name }}</li>
</ul></code>

In this example, we use item.id as the unique key.

Scope variables:

In a v-for loop, you can access the following scope variables:

• index: The index of the element in the array or object
• $index: The index of the element in the rendering list
• first: Whether the element is the first
• last: Whether the element is the last one
• even: Whether the index of the element is an even number
• odd : Whether the index of the element is an odd number

Tips:

##v-for can only be used to render lists. For conditional rendering, use
• v-if or v-else.
Always specify keys for child components in v-for loops.
• Scope variables can be used in templates but cannot be accessed in JavaScript.

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