Gain insights into practical CSS theming methods, delve into problem-solving, and discover the css-theming package to create highly customizable, dark mode-friendly apps in this course.

CSS isn’t what it used to be. Today, you’ll be hard-pressed to find a strong, straightforward, and expressive UI language that can beat modern CSS. As the tech world moves more and more towards web-based frameworks for UI, we start to see a bigger emphasis on highly customized looks for apps.

In this course, you'll learn how to properly develop apps that are theme aware. This course is split into two sections: in the first section, you will learn the practical methods and patterns around theming and discover common problems and their solutions. In the second section, you will get hands-on experience with the css-theming package and through it you'll learn how to customize every facet of your app. Most importantly, no matter the kind of app you're developing, users have come to expect dark mode support nowadays as a given.

By the end of this course you’ll be able to create stunning apps that are highly customizable by either applying what you learned in your own way or using the css-theming package.

CSS Theming for Professionals

The `design-values` module in `css-theming` gives you programmatic access to some of the CSS defined variables. You can, for example, obtain and display all the semantic colors in your app:

```javascript
import {
  getSemanticColorNames,
} from 'css-theming';

const semanticColorNames = getSemanticColorNames();
// Do whatever you want with `semanticColorNames`, it's an array of strings.
```

> **Note:** All modules are exported in css-theming so you can import `from 'css-theming'` instead of `from 'design-values'`;

Here are all the definitions you can obtain from `design-values`:

```
swatchNames
fgSwatchNames
colorNames
semanticColorNames
themeCssNames
```

## Obtaining defined themes

A common operation is displaying a list of your themes. For this we'll use the `getThemes` function. This returns an array of `Theme` objects, defined as:

```typescript
export interface Theme {
  category: string | null;
  name: string;
  cssName: string;
  brightness: Brightness;
}
```

So, `getThemes` might return something like:

```json
[{
  "name": "default",
  "category": "",
  "cssName": "theme-default",
  "brightness": "light"
}, {
  "name": "default-dark",
  "category": "",
  "cssName": "theme-default-dark",
  "brightness": "dark"
}]
```

The `design-values` module in `css-theming` gives you programmatic access to some of the CSS defined variables. You can, for example, obtain and display all the semantic colors in your app:

```javascript
import {
  getSemanticColorNames,
} from 'css-theming';

const semanticColorNames = getSemanticColorNames();
// Do whatever you want with `semanticColorNames`, it's an array of strings.
```

> **Note:** All modules are exported in css-theming so you can import `from 'css-theming'` instead of `from 'design-values'`;

Here are all the definitions you can obtain from `design-values`:

```
swatchNames
fgSwatchNames
colorNames
semanticColorNames
themeCssNames
```

# Obtaining defined themes

A common operation is displaying a list of your themes. For this we'll use the `getThemes` function. This returns an array of `Theme` objects, defined as:

```typescript
export interface Theme {
  category: string | null;
  name: string;
  cssName: string;
  brightness: Brightness;
}
```

So, `getThemes` might return something like:

```json
[{
  "name": "default",
  "category": "",
  "cssName": "theme-default",
  "brightness": "light"
}, {
  "name": "default-dark",
  "category": "",
  "cssName": "theme-default-dark",
  "brightness": "dark"
}]
```

This lesson shows how to programmatically access design values.

Before Getting Started

Theory

Using css-theming

Samples

Obtaining CSS Design Values