Vue hides judgment statements

Hiding judgment statements in Vue is one of the techniques often used in development, which can make the code more concise and clear. This article will introduce three hidden judgment statements commonly used in Vue.

1. v-if

v-if is the most commonly used hidden judgment statement in Vue. It judges whether an element is rendered based on the true or false expression. When the expression is true, the element is rendered, otherwise it is not rendered.

The syntax format of v-if is as follows:

<div v-if="flag">Hello,Vue!</div>

Among them, flag is a Boolean type data.

v-if also has a derivative instruction v-else, which is used to render elements when the v-if expression is false. v-else and v-if must be used closely, and the format is as follows:

<div v-if="flag">条件为真</div>
<div v-else>条件为假</div>

There is also a situation where when the expression of v-if is false, we may not want the element to be completely removed. Instead, if you want to keep the element in the DOM, you can use the v-show directive.

2. v-show

v-show is also used to control the display and hiding of elements based on the true or false expression, but it is different from v-if in that regardless of the expression Regardless of whether the expression is true or false, v-show will never remove elements.

The syntax format of v-show is as follows:

<div v-show="flag">Hello,Vue!</div>

3. v-for

The v-for instruction can loop through an array or object and add each element in it Render into the template. When the traversed data is an array, the syntax format of v-for is as follows:

<ul>
  <li v-for="(item,index) in list">{{item}}</li>
</ul>

Among them, item represents each element traversed, and index represents the index position of the element traversed.

When the traversed data is an object, the syntax format of v-for is as follows:

<ul>
  <li v-for="(value,key) in obj">{{key}} : {{value}}</li>
</ul>

Among them, value represents each attribute value in the object, and key represents each attribute name.

It should be noted that when using v-for loop, it is best to add a unique key value to each traversal item to improve rendering performance.

Summary

Through the above introduction, we can see that hidden judgment statements in Vue are very practical and can make our code more concise and clear. Among them, v-if, v-show and v-for are the three most commonly used hidden judgment statements. Being proficient in their use can improve development efficiency.

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