Less styleguide
##Naming Name variables descriptively. (bad: @white-color: #fff; good: title-color: #fff; )
##Nesting Avoid too much nested styles. Max 3-4 levels are recommended. Use comma-separated selectors with caution and only where it is really needed. Do not use comma-separated selectors nested in other comma-separated selectors.
##Mixins Use only parametrized mixins. Keep your mixins small.
##Included files Base files (files, which are included in other files) should contain only variables and parametrized mixind so they do not render to CSS.
##Lifted from http://primercss.io/guidelines/
Best practices and guidelines for writing HTML and CSS with approachable formatting, syntax, and more.
- Will be replaced with the ToC, excluding the "Contents" header {:toc}
- Paragraphs of text should always be placed in a
<p>
tag. Never use multiple<br>
tags. - Items in list form should always be in
<ul>
,<ol>
, or<dl>
. Never use a set of<div>
or<p>
. - Every form input that has text attached should utilize a
<label>
tag. Especially radio or checkbox elements. - Even though quotes around attributes is optional, always put quotes around attributes for readability.
- Avoid writing closing tag comments, like
<!-- /.element -->
. This just adds to page load time. Plus, most editors have indentation guides and open-close tag highlighting. - Avoid trailing slashes in self-closing elements. For example,
<br>
,<hr>
,<img>
, and<input>
. - Don't set
tabindex
manually—rely on the browser to set the order.
<p class="line-note" data-attribute="106">
This is my paragraph of special text.
</p>
Many attributes don't require a value to be set, like disabled
or checked
, so don't set them.
<input type="text" disabled>
<input type="checkbox" value="1" checked>
<select>
<option value="1" selected>1</option>
</select>
For more information, read the WhatWG section.
Whenever possible, avoid superfluous parent elements when writing HTML. Many times this requires iteration and refactoring, but produces less HTML. For example:
<!-- Not so great -->
<span class="avatar">
<img src="...">
</span>
<!-- Better -->
<img class="avatar" src="...">
- Lean towards radio or checkbox lists instead of select menus.
- Wrap radio and checkbox inputs and their text in
<label>
s. No need forfor
attributes here—the wrapping automatically associates the two. - Form buttons should always include an explicit
type
. Use primary buttons for thetype="submit"
button and regular buttons fortype="button"
. - The primary form button must come first in the DOM, especially for forms with multiple submit buttons. The visual order should be preserved with
float: right;
on each button.
Make use of <thead>
, <tfoot>
, <tbody>
, and <th>
tags (and scope
attribute) when appropriate. (Note: <tfoot>
goes above <tbody>
for speed reasons. You want the browser to load the footer before a table full of data.)
<table summary="This is a chart of invoices for 2011.">
<thead>
<tr>
<th scope="col">Table header 1</th>
<th scope="col">Table header 2</th>
</tr>
</thead>
<tfoot>
<tr>
<td>Table footer 1</td>
<td>Table footer 2</td>
</tr>
</tfoot>
<tbody>
<tr>
<td>Table data 1</td>
<td>Table data 2</td>
</tr>
</tbody>
</table>
- Use soft-tabs with a four space indent. Spaces are the only way to guarantee code renders the same in any person's environment.
- Put spaces after
:
in property declarations. - Put spaces before
{
in rule declarations. - Put line breaks between rulesets.
- When grouping selectors, keep individual selectors to a single line.
- Place closing braces of declaration blocks on a new line.
- Each declaration should appear on its own line for more accurate error reporting.
- Use hex color codes
#000
unless usingrgba()
. - Use
//
for comment blocks (instead of/* */
). - Avoid specifying units for zero values, e.g.,
margin: 0;
instead ofmargin: 0px;
. - Strive to limit use of shorthand declarations to instances where you must explicitly set all the available values.
As a rule of thumb, avoid unnecessary nesting in SCSS. At most, aim for three levels. If you cannot help it, step back and rethink your overall strategy (either the specificity needed, or the layout of the nesting).
Here are some good examples that apply the above guidelines:
// Example of good basic formatting practices
.styleguide-format {
color: #000;
background-color: rgba(0, 0, 0, .5);
border: 1px solid #0f0;
}
// Example of individual selectors getting their own lines (for error reporting)
.multiple,
.classes,
.get-new-lines {
display: block;
}
// Avoid unnecessary shorthand declarations
.not-so-good {
margin: 0 0 20px;
}
.good {
margin-bottom: 20px;
}
In general, the CSS file organization should follow something like this:
{% highlight bash %} styles ├── components │ ├── comments.scss │ └── listings.scss ├── globals │ ├── browser_helpers.scss │ ├── responsive_helpers.scss │ └── variables.scss ├── plugins │ ├── jquery.fancybox-1.3.4.css │ └── reset.scss ├── sections │ ├── issues.scss │ └── profile.scss └── shared ├── forms.scss └── markdown.scss
### Multiple bundles
Variations on this structure include the multi-bundle Rails approach, as seen in the `github/github` repo:
{% highlight bash %}
stylesheets
├── github
│ ├── base.scss
│ ├── layout.scss
│ └── buttons.scss
├── github2
│ ├── about.scss
│ └── blog.scss
└── mobile
├── _variables.scss
└── base.scss
Here, we have two desktop bundles to support IE9's maximum selector limit per CSS file, as well as a dedicated mobile bundle to go with our separate mobile views.
Use Sprockets to require files. However, you should explicitly import any scss that does not generate styles (globals/
) in the particular SCSS file you'll be needing it's helpers in. Here's a good example:
//= require_tree ./plugins
//= require my_awesome_styles
@import "../globals/basic";
.rule { ... }
This is also how Primer's styles are to be included, should you need them.
Use px
for font-size
, because it offers absolute control over text. Additionally, unit-less line-height
is preferred because it does not inherit a percentage value of its parent element, but instead is based on a multiplier of the font-size
.
Never reference js-
prefixed class names from CSS files. js-
are used exclusively from JS files.
Use the is-
prefix for state rules that are shared between CSS and JS.
Elements that occur exactly once inside a page should use IDs, otherwise, use classes. When in doubt, use a class name.
- Good candidates for ids: header, footer, modal popups.
- Bad candidates for ids: navigation, item listings, item view pages (ex: issue view).
When styling a component, start with an element + class namespace (prefer class names over ids), prefer direct descendant selectors by default, and use as little specificity as possible. Here is a good example:
<ul class="category-list">
<li class="item">Category 1</li>
<li class="item">Category 2</li>
<li class="item">Category 3</li>
</ul>
.category-list { // element + class namespace
// Direct descendant selector > for list items
> li {
list-style-type: disc;
}
// Minimal specificity for all links
a {
color: #f00;
}
}
- If you must use an id selector (
#selector
) make sure that you have no more than one in your rule declaration. A rule like#header .search #quicksearch { ... }
is considered harmful. - When modifying an existing element for a specific use, try to use specific class names. Instead of
.listings-layout.bigger
use rules like.listings-layout.listings-bigger
. Think aboutack/grep
ing your code in the future. - The class names
disabled
,mousedown
,danger
,hover
,selected
, andactive
should always be namespaced by a class (button.selected
is a good example).