How to Conditionally Apply a CSS Class in Vue.js

Conditionally Applying a CSS Class in Vue.js

There are times you need to change an element’s CSS classes at runtime. But when changing classes, it’s sometimes best to apply style details conditionally. For example, imagine your view has a pager. Pagers are often used to navigate larger sets of items. When navigating, it can be helpful to show the user the page they’re currently on. The style of the item is conditionally set, based on the current page that’s being viewed.

A pager in this case may look something like this:

Pager

In this example, there are five pages. Only one of these pages is selected at a time. If you built this pager with Bootstrap, the selected page would have a CSS class named active applied. You’d want this class applied only if the page was the currently viewed page. In other words, you’d want to conditionally apply the active CSS class. Luckily, Vue provides a way to conditionally apply a CSS class to an element, which I’m going to demonstrate in this article.

To conditionally apply a CSS class at runtime, you can bind to a JavaScript object. To successfully complete this task, you must complete two steps. First, you must ensure that your CSS class is defined. Then, you create the class bindings in your template. I’m going to explain each of these steps in detail in the rest of this article.

Step 1: Define Your CSS Classes

Imagine, for a moment, that the five page items shown in the image above were defined using the following HTML:

<div id="myApp">
  <nav aria-label="Page navigation example">
    <ul class="pagination">
      <li class="page-item"><a class="page-link" href="#">1</a></li>
      <li class="page-item"><a class="page-link" href="#">2</a></li>
      <li class="page-item active"><a class="page-link" href="#">3</a></li>
      <li class="page-item"><a class="page-link" href="#">4</a></li>
      <li class="page-item"><a class="page-link" href="#">5</a></li>
    </ul>
  </nav>
</div>

Notice that each page in this code snippet has a list-item element (<li …). That element references the page-item CSS class. In the code for this article, this class is defined in the Bootstrap CSS framework. However, if it weren’t defined there, it would be your responsibility to ensure that it was defined somewhere. The second CSS class is the one that’s most relevant to this article, though.

The active CSS class is used to identify the currently selected page. For this article, this CSS class is also defined in the Bootstrap CSS. As shown in the snippet above, the active class is only used in the third list item element. As you can probably guess, this is the CSS class that you want to apply conditionally. To do that, you need to add a JavaScript object.

The post How to Conditionally Apply a CSS Class in Vue.js appeared first on SitePoint.

Comments

Post a Comment

Popular posts from this blog

Visual Studio Code: A Power User’s Guide

Image
In this guide, you’ll learn how to take advantage of Visual Studio Code to supercharge your development workflow. This article is written for beginners who may be using Visual Studio Code for the first time. VS Code, as it’s commonly known, is considered a "lightweight" code editor. In comparison with full integrated development environment (IDE) editors which occupy gigabytes of disk space, VS Code only uses less than 200MB when installed. Despite the "lightweight" term, VS Code offers a massive number of features which keep increasing and improving with every new update. For this guide, we'll cover the most popularly used features. Every programmer has their own tool set which they keep updating whenever new workflows are discovered. If you want to learn every tool and feature VS Code has to offer, check out their official documentation . In addition, you may want to keep track of updates for new and improved features. Prerequisites In order to follow alo
Read more

6+ Best Websites for Free Fonts in 2020

Image
I firmly believe that, in order to strike the optimal balance between minimalism and visual appeal, a user interface should display no more than what’s absolutely necessary while making those necessary elements look visually appealing. Keep it simple, but make the simple look amazing. But, what does simple look like exactly? Well, strip away all of the over-the-top marketing gimmicks, redundant features, and cluttering visuals, and most of what’s left is the UI copy and text content. As boring as this sounds, let’s be honest: this is the most important aspect of any app or website. Information and the ability to navigate it is the entire reason users are using our app or website. So with the right typeface coupled with the right font styles (see “ Font vs typeface: the ultimate guide ”), we can create designs that are quite simple and yet visually appealing at the same time. This emphasizes the most important aspects of the design while usin
Read more

How to Contribute to Open Source TypeScript Projects

Image
If you think of the ideas of open source applied to information in an encyclopedia, you get to Wikipedia – lots and lots of small contributions that bubble up to something that’s meaningful. – Matt Mullenweg One of my favorite aspects of open source is the fact that anyone can contribute! It’s like “productive volunteering” (if you’ll humor me). It’s a fantastic way to build something bigger than you, give back to the community, and level up your skills. In this article, we’re going to talk about practical ways for you to get involved in open source TypeScript projects. We’ll first cover assessing your level then jump into how you can find opportunities. Assessing Your Level Before you get started contributing to open source, you want to find your comfort level. Where are you at skill-wise? What level of complexity are you wanting to solve? How much time do you want to spend? These are important questions to consider before diving in. This
Read more