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Dapper is a Javascript/TypeScript styling library (CSS-in-JS or CSS-in-TS). It features:

• Dynamic styles using modes, (i.e. in React, it styles based on props and state)

• TypeScript autocomplete and build-time checks

• Utilizes some of the best features of LESS/SASS CSS such as

  • nested styles
  • parent selectors

• CSS features such as

  • media queries
  • keyframes
  • pseudo classes and psuedo elements
  • auto-prefixing (for cross-browser compatibility)
  • unitless values (use 5 instead of '5px')
  • paddingHorizontal, paddingVertical, and same for margin

• Additional helpers to inject arbitrary CSS (great when styling 3rd party code)

npm install @convoy/dapper

Most examples are shown in TypeScript, but dapper works great with Javascript. TypeScript provides autocompletion of your styles and at build time checks that those styles exist.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    padding: 5,
  },
});

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    return (
      <div className={this.styles.root} />
    );
  }
}

Dapper generates a <style> element dynamically with autogenerated classes for each style rule.

The above generates the following CSS:

.dapper-root-a {
  padding: 5px;
}

Dapper enables dynamic styles using "modes", a series of functions that defines all the different "modes" or ways your component can look. This creates a nice separation of concerns removing a lot of if/else branching logic from your render function.

import * as dapper from '@convoy/dapper';

interface Props {
  highlight: boolean;
}

interface State {
  value: string;
}

const STYLES = dapper.compile({
  root: {
    backgroundColor: '#EEE',
    $highlight: {
      backgroundColor: '#FFF',
    },
  },
  input: {
    $tooLong: {
      color: 'red',
    },
  },
});

const MODES = {
  highlight: ({ props }: { props: Props }) => props.highlight,
  tooLong: ({ state }: { state: State }) => state.value.length > 8,
};

export default class Button extends React.Component<Props, State> {
  state = { value: '' };

  styles = dapper.reactTo(this, STYLES, MODES);

  render() {
    return (
      <div className={this.styles.root}>
        <input
          value={this.state.value}
          onChange={this._onChange}
        />
      </div>
    );
  }

  _onChange = ev => {
    this.setState({ value: ev.target.value });
  }
}

The above generates the following CSS:

.dapper-root-a {
  background-color: #EEE;
}

.dapper-root-highlight-b {
  background-color: #FFF;
}

.dapper-input-tooLong-c {
  color: red;
},

and applies clases like .dapper-input-highlight-b dynamically to the div if props.highlight is true, and similarly adds .dapper-input-tooLong-c to the input when state.value.length > 8.

CSS pseudo-selectors, such as :hover and :active and pseudo-elements such as ::before and ::after are supported as you might expect.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    ':hover': {
      backgroundColor: '#EEE',
    },
    '::after': {
      content: '"+"',
    },
  },
});

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    return (
      <div className={this.styles.root} />
    );
  }
}

The above generates the following CSS:

.dapper-root-a:hover {
  background-color: #EEE;
}

.dapper-root-a::after {
  content: "+";
}

Placeholders allow you to reference other styles names inside of a style rule. This can be helpful for cascading styles. Such as in this example, when child should look different when inside of parentA vs parentB.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  parentA: {
    '{child}': {
      backgroundColor: 'red',
    },
  },
  parentB: {
    '{child}': {
      backgroundColor: 'blue',
    },
  },
  child: {
    padding: 5,
  }
});

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    const { styles } = this;
    return (
      <div>
        <div className={styles.parentA}>
          <div className={styles.child} />
        </div>
        <div className={styles.parentB}>
          <div className={styles.child} />
        </div>
      </div>
    );
  }
}

The above generates the following CSS:

.dapper-parentA-a .dapper-child-c {
  background-color: red;
}

.dapper-parentB-b .dapper-child-c {
  background-color: blue;
}

.dapper-child-c {
  padding: 5px;
}

Parent selectors allow you to swap in the current selector into a new location in a selector. This is helpful when you want to prefix the generated classname for things like global classnames.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
 root: {
   'html.wf-loading &': {
     opacity: 0,
   },
 },
});

export default class Button extends React.Component<Props, State> {
 styles = dapper.reactTo(this, STYLES);

 render() {
   return (
     <div className={this.styles.root}>
       Hello World
     </div>
   );
 }
}

The above generates the following CSS:

html.wf-loading .dapper-root-a {
  opacity: 0,
}

Placeholders and parent selectors makes it easy to support things like styling child elements based on pseudo class selectors of parents, like hover. This helps avoid creating onMouseEnter, onMouseLeave handlers.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    padding: 5,
  },
  child: {
    '{root}:hover &': {
      backgroundColor: '#EEE',
    },
  },
});

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    return (
      <div className={this.styles.root}>
        <div className={this.styles.child} />
      </div>
    );
  }
}

The above generates the following CSS:

.dapper-root-a {
  padding: 5px;
}

.dapper-root-a:hover .dapper-child-b {
  background-color: #EEE;
}

Dapper supports media queries, including nested media queries.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    width: 200,
    '@media (max-width: 800px)': {
      '@media (orientation: landscape)': {
        width: 100,
      },
      '@media (orientation: portrait)': {
        width: 60,
      },
    },
  },
});

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    return (
      <div className={this.styles.root} />
    );
  }
}

The above generates the following CSS:

.dapper-root-a {
  width: 200px;
}
@media (max-width: 800px) and (orientation: landscape) {
  .dapper-root-a {
    width: 100px;
  }
}
@media (max-width: 800px) and (orientation: portrait) {
  .dapper-root-a {
    width: 60px;
  }
}

Media queries, modes and pseudo class/element selectors can be nested within CSS properties to make things more readable.

const STYLES = dapper.compile({
  root: {
    padding: {
      $small: 2,
      $medium: 4,
      $large: 8,
    },
    backgroundColor: {
      ':hover': '#EEE',
      ':focus': '#DDD',
    },
    width: {
      '@media (max-width: 500px)': 100,
      '@media (min-width: 500px)': 400,
    },
  },
});

The above generates the following CSS:

.dapper-root-a.dapper-root-small-b {
  padding: 2px;
}
.dapper-root-a.dapper-root-medium-b {
  padding: 4px;
}
.dapper-root-a.dapper-root-large-b {
  padding: 8px;
}
.dapper-root-a:hover {
  background-color: '#EEE';
}
.dapper-root-a:focus {
  background-color: '#DDD';
}
@media (max-width: 500px) {
  .dapper-root-a {
    width: 100px;
  }
}
@media (min-width: 500px) {
  .dapper-root-a {
    width: 400px;
  }
}

Dappers keyframes function generates CSS animation names which can then be referenced in styles.

import * as dapper from '@convoy/dapper';

const fadeOut = dapper.keyframes({
  '0%': {
    opacity: 0,
  },
  '100%': {
    opacity: 1,
  },
});

const STYLES = dapper.compile({
  root: {
    animation: `5s ${fadeOut} linear`,
  },
});

The above generates the following CSS:

@keyframes dapper-anim-a {
  0% {
    opacity: 0;
  }
  100% {
    opacity: 1;
  }
}
.dapper-root-a {
  animation: 5s dapper-anim-a linear;
}

Dapper supports easy ways to add the same padding and margin on to the top and bottom or the left and right using paddingHorizontal and paddingVertical or the margin equivalents.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    paddingHorizontal: 4,
    paddingVertical: 8,
  },
});

The above generates the following CSS:

.dapper-root-a {
  padding-left: 4px;
  padding-right: 4px;
  padding-top: 8px;
  padding-bottom: 8px;
}

Sometimes you need to add arbitrary CSS to a document, such as when you are working with a third party library that controls its portion of the DOM tree.

dapper.renderStatic({
  'html, body': {
    backgroundColor: '#CCFFFF',
    '@media (max-width: 800px)': {
      backgroundColor: '#FFCCFF',
    },
  },
  '.pac-container': {
    backgroundColor: '#EEE',
  },
});

The above generates the following CSS:

html, body {
  background-color: #CCFFFF;
}
@media (max-width: 800px) {
  html, body {
    background-color: #FFCCFF;
  }
}
.pac-container {
  background-color: #EEE;
}

Dapper works out of the box without any configuration needed. The default configuration can overridden globally however, by providing one or many of the following parameters:

node (optional): The style element to render styles into. Default is a newly created style element appended to document.head.

classNamePrefix (optional): The prefix to add all generated classnames. Default if process.env.NODE_ENV === 'production' is d-, otherwise the default is dapper-.

friendlyClassNames (optional): A flag dictating that all generated classnames use the full key path of the style, making it easy to identify in browser dev tools where in code is responsible for a style. Default if process.env.NODE_ENV === 'production' is false, otherwise the default is true.

useInsertRule (optional): A flag dictating that when rendering to the style element whether to use CSSStyleSheet.insertRule or innerHTML. Using insertRule is faster because it means the browser has less to repeatedly parse, but is more difficult to inspect using browser dev tools. Default if process.env.NODE_ENV === 'production' is true, otherwise the default is false.

dapper.configure({
  node: document.querySelector('#stylesheet'),
  classNamePrefix: 'app-',
  friendlyClassNames: false,
  useInsertRule: true,
})

Configuration can also be used per call to compile, keyframes and renderStatic to override the global configuration. This can be useful when you want to render to a different element which allows you to separately unload those styles.

dapper.compile({
  root: {
    padding: 5,
  },
}, {
  node: document.querySelector('#styles'),
});

Dapper exposes a compute function which takes the output of compile, any functions that define the modes and an object that defines the current state to compute the modes with and returns the classnames of the various styles. This function is useful even outside of React contexts or when rendering items in a list which have their own modes that aren't based directly on props or state. In React, we primarily use reactTo, which is a simple wrapper around compute that uses the component as the state to compute modes from.

import * as dapper from '@convoy/dapper';

const STYLES = dapper.compile({
  root: {
    width: 200,
  },
});

const ITEM_STYLES = dapper.compile({
  root: {
    backgroundColor: '#CCC',
  },
});

const ITEM_MODES = {
  highlight: (item: Item) => item.highlight,
};

export default class Button extends React.Component<Props, State> {
  styles = dapper.reactTo(this, STYLES);

  render() {
    return (
      <div className={this.styles.root}>
        {this.props.items.map(this._renderItem)}
      </div>
    );
  }

  _renderItem(item) {
    const styles = dapper.compute(ITEM_STYLES, ITEM_MODES, item);
    return (
      <div className={styles.root}>
        {item.label}
      </div>
    );
  }
}

1. Switch to the right node: nvm install
2. Install the dependencies: npm install
3. Watch for changes: npm start