Styling your app can get difficult as the number of components grows and you begin to reuse components in different scenarios. This blog post goes through the ultimate way to style your base components to allow easy extensibility throughout your Ember app.
+image: +imageAlt: +--- + +Foreword: Should out to +[Florian Pichler](https://mainmatter.com/blog/author/pichfl) for introducing me +to this pattern earlier this year. + +## What is the issue? + +When creating a component library or any kind of UI kit for your Ember app, +you’ll most likely want to have basic components that can then be extended and +styled based on their usage. + +The majority of modern JS frameworks come with some flavour of CSS modules, +meaning you can style your component once and reuse that component everywhere +you need it without having the styles leaking across your app. Unfortunately +Ember doesn’t come with this functionality built in, but we do have +[ember-css-modules](https://github.com/salsify/ember-css-modules) that handles +this for us. + +The point in which this starts to become tricky is when we start to deeply nest +our components, styling it slightly differently at each level. + +For example, we can have a base `Button` component that removes the default +browser styles and sets some very simple styling and functionality that can be +shared across every button in our app. An example of this could be disabling the +button when a “loading” state is truthy. We could then have a `PrimaryButton` +which would extend our base `Button` and give it some styles to reflect the +aesthetic of our app. Finally, we could have a `Card` component that uses this +`PrimaryButton`, but we actually want it to have slightly less padding and +change the `border-radius`. + +So in this scenario, it wouldn’t be unlikely to have the padding for a single +element set at three different levels, meaning that we would need to be very +careful about the selectors we are using to make sure we are setting the styles +without doing anything that might be impossible to override if we wanted to +extend our `Card` component later on: I’m looking at you `!important`. + +## What is the solution? + +**Where** is the solution! Well, to be more specific - **_":where()”_** is the +solution. `:where()` is a CSS pseudo-class function that was widely adopted by +all major browsers in 2021 and allows us to pass in a list of selectors to +attach our styles to, but with one major benefit: the specificity of `:where()` +is always 0,0,0. This means that no matter how many selectors we use with our +`:where()`, the styles will still be super simple to override. This is perfect +for our scenario, where we want to have a simple base component that is easily +overridden elsewhere in our app. + +Lets look at how this would work: + +### Button component + + + +```html +{% raw %} +// button.hbs + +{% endraw %} +``` + +Going through this component quickly: + +- `...attributes` allows us to add element properties from the consuming + component, +- `data-button` allows us to drill the CSS regardless of how far away from this + component we are (more on that later), +- `data-loading` allows us to style the component based on that boolean rather + than having to add dynamic styles (i.e. {% raw %} + `local-class=”{{if @loading 'loading'}}”` {% endraw %}), this is a personal + preference but I much prefer styling state in this way, +- `local-class` comes from + [ember-css-modules](https://github.com/salsify/ember-css-modules) and allows + us to scope a class to a component, +- the other two should be fairly self explanatory for anyone with knowledge of + HTML and [ember-modifier](https://github.com/ember-modifier/ember-modifier)- + +```css +// button.css +.button[type="button"] { + /* styles that we don't want to easily override */ + user-select: none; + cursor: pointer; +} + +.button[data-loading] { + pointer-events: none; + background-color: gray; +} + +:where(.button) { + /* remove all browser styling */ + all: unset; + + /* set our own styles that can be easily overriden */ + padding: 5px; + border-radius: 2px; +} +``` + +Going through this stylesheet we can see the different styling strategies at +play. + +`.button[type="button"]` gives as a specificity of (0,2,0) making it is slightly +more difficult to override elsewhere. This is intentional as we shouldn’t really +be overriding these as they are base styles for the button. + + + +> For anyone that didn’t know, if you open up the Inspector in Safari or Chrome +> and hover over the CSS selector, it will tell you the specificity. +> Unfortunately I couldn’t see how to do this on Firefox. + +`.button[data-loading]` has the same specificity as above for the same reasons. +It also showcases how simple it is to pass a state from the `hbs` to the +stylesheet so that you can style the component based on that. In this scenario +we are removing the `pointer-events` and updating the `background-color` . + +And then we come to the main event: `:where(.button)` is being used to reset the +browser styles with `all: unset` and then we add our own styles that we want to +be easily overridden. In this scenario we are adding a small `padding` and a +little `border-radius` , this means that anywhere using the `Button` component +will have these styles baked in, but they are very easy to override and that is +because… (drumroll please) + + + +The specificity is (0,0,0)! We don’t need to add any additional classes or jump +through any hoops to override these styles, but these defaults will always be +available if we weren’t to add any additional styles. + +### PrimaryButton component + + + +```html +{% raw %} // primary-button.hbs + +{% endraw %} +``` + +Here we are using the base `Button` component from before and updating the +styles to give it more of a theme. + +```css +/* styles we want to be harder to override */ +.primary-button { + background-color: lightblue; +} + +/* styles we want to be easy to override */ +:where(.primary-button) { + padding: 10px 25px; +} +``` + +Similarly to before, we’ve split the component styles into two sections: + +1. the styles we want to be harder to override, +2. the styles we want to be easy to override. + +(Of course, these styles are just an example and not how any app should look). + +As you can see we want our `PrimaryButton` to be stronger about wanting to be +`lightblue` and therefore we are adding a specificity of (0,1,0) by adding the +class name here. + +On the other hand, we are insinuating that we expect the `padding` to change +more often by the usage of `:where()` . + +### Card component + + + +```html +{% raw %} +