Vue Js Classes

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You’re browsing the documentation for v2.x and earlier.

For v3.x, click here. A common need for data binding is manipulating an element’s class list and its inline styles. Since they are both attributes, we can use v-bind to handle them: we only need to calculate a final string with our expressions.

However, meddling with string concatenation is annoying and error-prone. For this reason, Vue provides special enhancements when v-bind is used with class and style.

In addition to strings, the expressions can also evaluate to objects or arrays. We can pass an object to v-bind:class to dynamically toggle classes:. The above syntax means the presence of the active class will be determined by the truthiness of the data property isActive.

You can have multiple classes toggled by having more fields in the object. In addition, the v-bind:class directive can also co-exist with the plain class attribute.

So given the following template:. And the following data:. It will render:. When isActive or hasError changes, the class list will be updated accordingly.

For example, if hasError becomes true, the class list will become "static active text-danger".

  1. The bound object doesn’t have to be inline:.

This will render the same result. We can also bind to a computed property that returns an object. This is a common and powerful pattern:.

We can pass an array to v-bind:class to apply a list of classes:. Which will render:. If you would like to also toggle a class in the list conditionally, you can do it with a ternary expression:.

This will always apply errorClass, but will only apply activeClass when isActive is truthy.

However, this can be a bit verbose if you have multiple conditional classes. That’s why it’s also possible to use the object syntax inside array syntax:.

This section assumes knowledge of Vue Components. Feel free to skip it and come back later.

When you use the class attribute on a custom component, those classes will be added to the component’s root element.