The first item in the vue drop-down box does not display

Vue is a popular JavaScript framework that is often used to build single-page applications (SPA). In Vue, a drop-down box is a common UI component that can be used to allow users to select one or more options. However, sometimes we encounter such a problem: the first item of the drop-down box is not displayed. This article will describe common solutions.

1. Check the data source

Generally speaking, the options of the drop-down box are obtained from the data source, such as an array or an API interface. If the first item in the data source is incorrect or has a null value, it will not be displayed in the drop-down box. Therefore, we need to check that the data source is correct, that the first item is not empty, and that the data type is correct.

2. Check the rendering code

Generally, the rendering of the drop-down box is completed through the v-for instruction. If the v-for directive is set on the wrong label, or the loop starts on the second item of the array, the first item will not be rendered. Therefore, we need to check whether the rendering code is correct.

3. Check CSS style

The style of the drop-down box may also cause the first item not to be displayed. If the display:none or visibility:hidden attribute is set in the CSS style, the first item of the drop-down box will be hidden. Therefore, we need to check the CSS style to make sure the first item is not hidden.

4. Using the v-model directive

In some cases, the first item may not be displayed because the v-model directive is not set correctly. The v-model directive can bind the value in the drop-down box to the data in the Vue instance. If the v-model directive is not set correctly, the data in the Vue instance may not be updated synchronously with the value in the drop-down box. Therefore, we need to ensure that the v-model directive is set correctly and that the data of the Vue instance is correctly bound to the v-model.

5. Make sure the component is loaded

In some cases, the first item may not be displayed because the drop-down box component has not been loaded correctly. This may be caused by asynchronous loading or lazy loading. In this case, we need to ensure that the Vue component has been loaded correctly and there are no asynchronous loading issues.

Summary

In Vue, the drop-down box is a common UI component. If you encounter the problem that the first item of the drop-down box is not displayed, you can solve it by checking the data source, rendering code, CSS style, v-model directive and component loading. In actual development, the code needs to be carefully checked to ensure that the drop-down box is displayed correctly.

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