The difference between v-show directive and v-if directive in Vue documentation

Vue.js is a popular JavaScript framework that uses a data-driven approach to create interactive web applications. Vue.js provides many instructions in the documentation, among which the v-show instruction and the v-if instruction are two common instructions. Although these two instructions look similar, their purpose and implementation are somewhat different. In this article, we will discuss the difference between v-show instruction and v-if instruction in detail.

1. v-show directive

The v-show directive is a directive in Vue.js, which is used to control the display or hiding of an element. When the value of v-show is true, the element will be displayed. When the value of v-show is false, the element will be hidden. The v-show directive does not remove the element from the DOM, but controls the display or hiding of the element through the CSS display attribute. So when an element is hidden, it still takes up space on the page.

The syntax of the v-show instruction is as follows:

...

where expression is an expression used to calculate whether the element is displayed or hidden. If the value of expression is true, the element will be displayed; if the value of expression is false, the element will be hidden.

The advantage of the v-show directive is that it switches between showing and hiding an element without re-rendering the entire component. This makes the v-show directive more suitable for use on elements that need to frequently switch display states.

2. v-if directive

The v-if directive is another directive in Vue.js. It is used to control whether an element is added to the DOM. When the value of v-if is true, the element is added to the DOM; when the value of v-if is false, the element is removed from the DOM. Therefore, when an element is hidden, it does not take up space on the page.

The syntax of the v-if directive is as follows:

...

Among them, expression is an expression used to determine whether an element is added to the DOM. If the value of expression is true, the element will be added to the DOM; if the value of expression is false, the element will not be added to the DOM.

The advantage of the v-if directive is that it can reduce the number of DOM elements, thereby improving the performance of web applications. When an element is removed, it does not occupy memory, which can reduce the load time and memory footprint of the page. Therefore, the v-if directive is more suitable for use on elements that need to be switched or loaded frequently.

3. The difference between the v-show instruction and the v-if instruction

Although both the v-show instruction and the v-if instruction can control the display or hiding of elements, their implementation methods are different. The v-show directive controls the display or hiding of elements through the display attribute of CSS, while the v-if directive controls the display or hiding of elements by deleting or adding DOM elements. Therefore, in some cases, it is more appropriate to use the v-show directive than the v-if directive, and vice versa.

In addition, the v-show directive is simpler and faster than the v-if directive because it simply switches the display or hiding of the element without re-rendering the entire component. But at the same time, the v-if directive can reduce the number of DOM elements, thereby improving the performance of web applications. Therefore, when using these two instructions, you need to pay attention to their applicable scenarios and performance impact.

4. Conclusion

In Vue.js, both the v-show directive and the v-if directive can be used to control the display or hiding of elements. Although their implementation is somewhat different, the difference in usage is not significant. Therefore, when using these two instructions, you need to choose which one to use based on the actual situation. On some elements that need to frequently switch their display state, you can use the v-show directive; on some elements that need to be frequently switched or loaded, you can use the v-if directive. No matter which directive is used, you need to pay attention to their applicable scenarios and performance impact in order to improve the performance and user experience of web applications.

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