Using css variables in react

CSS variables are really cool.

using css variables in react

You can use them for a lot of things, one of which is applying themes in your application with ease. CSS variables are a way for us to define variables, that will be applied throughout our application. The syntax is as follows:. What happens here? Seems really simple?

Because it is. According to caniuse. If you want to read more, you can find more information in the MDN page. Setting and using CSS variables from javascript is just as easy as setting and using them in css. To get a value defined on an element:.

Will give us the value of the primary custom css property defined for the element. And now the light property will be accessible to all of our code. The React Context API is the only way provided by react to pass props indirectly from one component to a descendent component. The parameters passed to the React. A Voila! No matter where in the component hierarchy our component lies, it has access to the themeName variable.

If we want to allow editing the value in our context, we can pass a function like so:. This just happens to be the color pallette I use for my blog, but really the sky is the limit when it comes to themes, so feel free to experiment. In this component we store our selected theme object, and the selected theme name, and we defined a function to toggle our selected theme.

The last bit left is actually setting the css custom properties from our theme. We can easily do it using the.

using css variables in react

Now for each value in our theme object we can access a css property with the same name prefixed with -- of course. The last thing we need is to run the setCSSVariables function every time the theme is toggled, so in our Theme component we can use the useEffect hook like so:. The full source can be found on github. Clicking the Toggle will call the toggleTheme function, and will update our theme for the entire app, no more configuration needed. If you want to see a real live example, you can check out the source code of my blog.

I'm Dor Shinar. I am a web developer, who also likes to write articles.

CSS Variables

This is my blog! The syntax is as follows: What happens here?We you! Lets start with the code from our last post :. If you had to guess, how do you think one would go about doing this? Lets distill our question down into something we could search Google with.

To render a Javascript expression in JSX, all you need to do is surround the expression in curly braces, like so:. React's render method is just a regular old method, which means that it can contain variables, functions, and any other code required to make your view render.

Considering our circumstances, this seems like an apt place to define targetOfGreeting :. The last thing worth mentioning is how you can use Javascript expressions to populate HTML attributes. A great example of this is programmatically setting CSS classes, which can be done like so:.

You can check out the working code here! There are two things worth noting about the code above. The first is that we wrapped our return statement in parentheses because it spans multiple lines, which is considered best practice. It may take a little getting used to, but when you write React components you will always use className instead of class.

Sign in with Github. In this post we explore the various ways we variables can be rendered in JSX. Eric Simons React.

Help spread the word about this tutorial! Join our mission to Spread Knowledge.When building React applications or any application actuallywe need it to look great. For web applications, the standard beautification language is called CSS. Since the age of the dinosaurs, properly structuring CSS styles and arranging them has always been a problem.

In small apps, this is not really a problem, but with applications of larger structure, things are bound to get real hazy. With large projects that have extended sections and features, it becomes a real menace to deal with.

At scale these problems become real scale here referring to a codebase with many developers working on itbut then there are a couple of problems that we have to take into account and make sure we understand before we attempt to solve them.

Some of the problems are: 1. Dead code elimination. CSS is a language of globals. Global CSS can easily rewrite styling in other classes. A change in the style in one class can ultimately and silently change the UI on multiple components. Generally, no one wants that to happen when they develop apps.

Most times while building apps, we have styling that is redundant or no longer in use. Although they can be small at first, over time it builds up and we have rogue and unused CSS everywhere and it can cause unnecessarily large file sizes. With CSS modules, we get to only import styles we use. Working with dependencies in CSS is hazy.

Most of the time we are used to just including the entire script directly into the page whether they are being used or not. Sometimes you need your CSS class to style in a certain way in one section and in a different way in another section.

In this case, it is usually better to have the CSS class variable modifiable in the component. Modular CSS solves each of these problems in a clean structured manner by having our components import only the classes they actually use therefore getting rid of redundancy.

This in itself also solves the problems of global namespaces. CSS written as JavaScript objects can be leveraged directly in React components by using the style attribute on components.

The code above is a clear example of using CSS as a JavaScript object and it allows us to have styling that is unique to that element. Another thing you can do when defining the CSS as a JavaScript object is use variables as the values for the style property.

Making Rainbows 🌈 with CSS Variables and React

In this way it can change depending on some conditions:. CSS modules are not very different from the method above. However, this in itself will not work and we will need to configure our loader to make it work. Most of the configuration for our application to work with CSS modules will be done in the webpack configuration file. So assuming you have set up a React application using create-react-appyou will need to take control of the configuration of your app using the eject command:.

With normal apps not created using create-react-app you can configure Webpack in a similar way as shown in this article. After ejecting, we can update our webpack. In the webpack configuration file, replace the content below:. With the change, we can now use CSS modules in our project. We have also set up hashing to properly generate names for the classes being used in the modules.

You can use a shorthand to specify the same loader like so: loader: 'css? If you are not using create-react-appadding the required options and setting up the extractTextPlugin will be the way to set up CSS Modules:. You can install this via the npm registry:. The demo implements CSS Modules, with every component implementing its own style.

You can download the demo on GitHub. Next, we installed the react-css-modules package by running the command below in our terminal:.The var function can be used to insert the value of a custom property. For a global scope you can use either the :root or the body selector. The following example first defines a global custom property named "--main-bg-color", then it uses the var function to insert the value of the custom property later in the style sheet:. If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:.

Margins Margin Collapse. Float Clear Float Examples. Navbar Vertical Navbar Horizontal Navbar. Function var HOW TO.

using css variables in react

Your message has been sent to W3Schools. W3Schools is optimized for learning, testing, and training. Examples might be simplified to improve reading and basic understanding.

Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using this site, you agree to have read and accepted our terms of usecookie and privacy policy. Copyright by Refsnes Data. All Rights Reserved. Powered by W3.I added an easter egg to my blog last week. We then promote it to its own composite layer using backface-visibility: hidden.

This will mitigate any scrolling issues. We cannot see the color underneath. To fix this, we need to grayscale the image, invert the colors, and then add an opacity.

We do all of this via CSS:. Looking good!

using css variables in react

Now it looks right! What can we do about that? The difference with CSS Variables is that they can be changed at runtime. Variables are always prepended with double-hyphens. Then we can change around the background color, and the linear-gradient using the var function. This means that we can change the any of these values individually. We can use an online color converter to convert from deepskyblue to HSLA.

We pass the event object into this method. For performance reasons, we only want the event listener to be active when the mouse button is actively being pressed. To do this, we set up handleMouseDown and handleMouseUp methods that will be called when the mousedown and mouseup events are triggered.

We again pass the event object to the handleMouseDown method. We need to check if the initial click target which is e. This is what verifies that the user initially clicked on the background before they started dragging their mouse. We use the element. We then pass in a selector. This blog uses Emotion JS to handle styling, so we have to pass in the same layoutStyles variable that we pass to Emotion. A couple of notes here:. Only if those selectors do not match, do we change the mousedown state and add an event listener for mousemove.

We also have a method for handling the mouseup event that changes state and removes the event listener for performance reasons when the user stops pressing the mouse.

Changing CSS variable with JavaScript

We now have our mousemove event listener set up, but we still need event listeners for the mouseup and mousedown events. From these event listeners, we call the handleMouseDown and handleMouseUp events, which can then create the mousemove event listener.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Already on GitHub? Sign in to your account. I have a React component that is using css-modules.

Rendering Variables in React components

Is there a way for me to get access to the SASS variables used in the css-module? My styles. My files look something like this note the comment for use-case :. Speaking to geelen we first tried using value by adding the following line to styles. I would've expected something more like this for index. Typo on my behalf, thanks for pointing it out. Edited above. Thank you axelson and hadimichael Just tried it! And it works well! Only drawback, it breaks webpack HMR when I modify one of my css file.

This is due to :export. Any idea how to make it works with HMR? I'm thinking of something like that I use fro my reducers :. Awesome work guys! Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Jump to bottom. Copy link Quote reply. My files look something like this note the comment for use-case : index.

I want that variable to come from my imported styles file i. This comment has been minimized.I also really like CSS. You're writing CSS either way! It's just packaged a little bit differently. No matter where you put your CSS, it behooves you to develop a mastery of the language.

Becoming better at CSS will make you a more effective front-end developer. We'll see how we can use them in our React apps to improve our workflows and do some pretty fancy stuff.

As a React developer, you might be thinking that you don't need variables in CSS. You have an entire Javascript engine at your disposal! There are two reasons to switch to CSS variables in your React app:. Let's look at how to use them, and then we'll see what doors get unlocked! The funky thing is that they look just like properties; in fact, the reason that they're officially called "CSS Custom Properties" is because they are properties, just like position or color.

We can define our own properties now. By hanging our custom properties on the root html tag, we ensure that they can be accessed anywhere in our app. Let's see what this looks like in React. This tutorial uses styled-components styled-componentsbut the instructions should be relatively similar regardless of the CSS-in-JS library.

First, I'm going to assume that you have a file that holds all of your design tokens, something like this:. In a React app, you might import them directly into the components that need them:. We've created some variables, hung them on the root node, and now we can access them in our components:.

This is a nice little win, in my opinion. Being able to access theme values without an import or an inline function is a breath of fresh air. You do lose some static typing benefits—more on this later—but it's a very happy tradeoff in my eyes. This is a relatively minor difference, though. Let's look at something more interesting…. It looks pretty, but we get feedback that the click target is too small on mobile devices: industry guidelines are that interactive elements should be between 44px and 48px tall 44px and 48px tall.

We need to bump up the size to make it easier to tap on phones. Let's walk through a possible solution, not using CSS variables. We ship this change, and we sleep a little bit better knowing that we've improved the usability of our app. We quickly learn that our work isn't done, however. Buttons are not the only tappable elements in our apps!


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