Description
This is a brief description of how the common theme is structured using both BEM and SASS 7-1 systems and how to use them.
7-1 pattern
File structure
SCSS files are structured following the 7-1 pattern.
@rveitch made a great summary with the following, which can also be found here.
Note: Folders with an * are customizations we made to the original 7-1 pattern to best fit our needs
css/common/
|
|– utils/
| |– variables/ # Sass Variables used in Functions, Mixins, Helpers, ...
| | |- colors/
| | | |- _base.scss
| | | |- _base-palette.scss # Base colors used everywhere
| | | |- _lifecycle-palette.scss # Colors used for lifecycle of an object (e.g. representing states such as new, frozen, done, ...), based on the base colors
| | | |- _semantic-palette.scss # Colors used for semantic meaning (e.g. red for errors, green for success, ...), based on the base colors
| | | ...
| | |
| | |- _depression.scss
| | |- _elevation.scss
| | |- _size.scss # Base sizes used everywhere (spacings, ...)
| | |- _spacing.scss
| | |- _typography.scss # Typography sizes, weights, families, ...
| | ...
| |
| |– functions/ # Sass Functions
| | |- _color.scss # Color manipulation functions
| |
| |– mixins/ # Sass Mixins
| |– helpers/ # Class & placeholders helpers
|
|– vendors/ # Third-party libs, should be either:
| # - Overload of the lib SCSS variables (BEST way, but possible only if the lib exposes them. e.g. Bulma)
| # - Overload of the lib necessary CSS classes only (not great as it duplicates some rules in the browser, which add weight and computation. e.g. dataTables)
| # - Duplicate the lib CSS completly to insert SCSS variables (not great as it will be outdated when updating the lib itself. e.g. jQuery UI)
| |– _bulma-variables-overload.scss # Bulma CSS framework
| |– _jquery-ui.scss # jQuery UI
| ... # Etc…
|
|– base/
| |– _reset.scss # Reset/normalize
| |– _typography.scss # Typography fonts imports
| ... # Etc…
|
|- _shame.scss # Shame file, should contain all the ugly hacks (https://sass-guidelin.es/#shame-file)
`– main.scss # Main Sass file
Usage
To avoid common errors, files should be imported in the final file in the following order. Again those are just following the SASS guidelines:
- Utils
- Variables
- Functions
- Mixins
- Helpers
- Vendors
- Base
- Shame file
BEM methodology
Principles
BEM is a methodology that helps you to create reusable components and code sharing in front‑end development.
The main idea is to use discriminant classes instead of nested basic selectors for 2 main reasons:
- It's easier to understand the purpose of a specific class when seeing it in the HTML markup of the SCSS file
- It's easier to override a specific class when needed as you don't need to use a selector at least as precise/complex as the one you want to override
In our implementation, we start with the code of the UI block, followed by the sub-element, then the property or modifier. Separation is made of -- instead of __.
Examples
Classes and CSS properties example
// SCSS variables:
// - For CSS properties: CSS class, followed by CSS property
$common-button--padding-y: 6px !default;
$common-button--padding-x: 9px !default;
$common-button--border: 0 !default;
$common-button--border-radius: $common-border-radius-400 !default;
$common-button--box-shadow-bottom: 0px 2px 0px !default;
$common-button--box-shadow-top: inset 0px 2px 0px !default;
$common-button--label--margin-left: $common-spacing-200 !default;
States example
// SCSS variables:
// Same rule as before, but with a `--is-` or `--on--` suffix
$common-quick-create--input--padding: $common-spacing-0 default;
$common-quick-create--input--padding-x--is-opened: $common-spacing-300 !default;
$common-quick-create--input--padding-y--is-opened: $common-spacing-300 !default;
$common-quick-create--input--width: $common-size-0 !default;
$common-quick-create--input--width--is-opened: 245px !default;
$common-quick-create--input--background-color: $common-color-white-100 !default;
$common-quick-create--input--background-color--on-hover: $common-color-grey-200 !default;