Stylus选择器(Selectors)

缩排(Indentation)

Stylus蛮“玄幻”的(如基于缩进),空格有重要的意义,所以,我们使用缩排和凹排代替花括号{}:

body
  color white

上面代码就对应于:

body {
  color: #fff;
}

如果你喜欢,你可以把冒号加上,分隔属性和值,便于阅读:

body
  color: white

规则集

Stylus就跟CSS一样,允许你使用逗号为多个选择器同时定义属性:

textarea, input
  border 1px solid #eee

使用新行是一样的效果:

textarea
input
  border 1px solid #eee

他们都将会编译为:

textarea,
input {
  border: 1px solid #eee;
}

该规则唯一的例外就是长得像属性的选择器。例如,下面的foo bar baz可能是个属性或者是选择器。

foo bar baz
> input
  border 1px solid

为解决这个原因,我们可以在尾部加个逗号:

foo bar baz,
form input,
> a
  border 1px solid

父级引用

字符&指向父选择器。下面这个例子,我们两个选择器(textareainput)在:hover伪类选择器上都改变了color值:

textarea
input
  color #A7A7A7
  &:hover
    color #000

编译为:

textarea,
input {
  color: #a7a7a7;
}
textarea:hover,
input:hover {
  color: #000;
}

下面这个例子,IE浏览器利用了父级引用以及混合书写来实现2px的边框:

box-shadow()
  -webkit-box-shadow arguments
  -moz-box-shadow arguments
  box-shadow arguments
  html.ie8 &,
  html.ie7 &,
  html.ie6 &
    border 2px solid arguments[length(arguments) - 1]

body
  #login
    box-shadow 1px 1px 3px #eee

将会被编译为:

body #login {
  -webkit-box-shadow: 1px 1px 3px #eee;
  -moz-box-shadow: 1px 1px 3px #eee;
  box-shadow: 1px 1px 3px #eee;
}
html.ie8 body #login,
html.ie7 body #login,
html.ie6 body #login {
  border: 2px solid #eee;
}

如果您需要在选择器中使用&符号而不像父引用那样,则可以将其转义:

.foo[title*='\&']
// => .foo[title*='&']

部分引用(Partial Reference)

^[N] anywhere in a selector, where N can be a number, represents a partial reference.

Partial reference works similar to the parent reference, but while parent reference contains the whole selector, partial selectors contain only the first merged N levels of the nested selectors, so you could access those nesting levels individually.

The ^[0] would give you the selector from the first level, the ^[1] would give you the rendered selector from the second level and so on:

.foo
&__bar
width: 10px

^[0]:hover &
width: 20px

这将渲染为如下CSS:

.foo__bar {
width: 10px;
}
.foo:hover .foo__bar {
width: 20px;
}

Negative values are counting from the end, so ^[-1] would give you the last selector from the chain before &:

.foo
&__bar
&_baz
width: 10px

^[-1]:hover &
width: 20px

would be rendered as

.foo__bar_baz {
  width: 10px;
}
.foo__bar:hover .foo__bar_baz {
  width: 20px;
}

Negative values are especially helpful for usage inside mixins when you don’t know at what nesting level you’re calling it.


Note that partial reference contain the whole rendered chain of selectors until the given nesting level, not the “part” of the selector.

部分引用中的范围

^[N..M] anywhere in a selector, where both N and M can be numbers, represents a partial reference.

If you’d have a case when you’d need to get the raw part of the selector, or to get the range of parts programmatically, you could use ranges inside partial reference.

If the range would start from the positive value, the result won’t contain the selectors of the previous levels and you’d get the result as if the selectors of those levels were inserted at the root of the stylesheet with the combinators omitted:

.foo
  & .bar
    width: 10px

    ^[0]:hover ^[1..-1]
      width: 20px

would be rendered as

.foo .bar {
  width: 10px;
}
.foo:hover .bar {
  width: 20px;
}

One number in the range would be the start index, the second — the end index. Note that the order of those numbers won’t matter as the selectors would always render from the first levels to the last, so ^[1..-1] would be equal to the ^[-1..1].

When both numbers are equal, the result would be just one raw level of a selector, so you could replace ^[1..-1] in a previous example to ^[-1..-1], and it would be equal to the same last one raw selector, but would be more reliable if used inside mixins.

Initial Reference

The ~/ characters at the start of a selector can be used to point at the selector at the first nesting and could be considered as a shortcut to ^[0]. The only drawback is that you can use initial reference only at the start of a selector:

.block
&__element
~/:hover &
color: red

Would be rendered as

.block:hover .block__element {
color: #f00;
}

Relative Reference

The ../ characters at the start of a selector mark a relative reference, which points to the previous to the & compiled selector. You can nest relative reference: ../../ to get deeper levels, but note that it can be used only at the start of the selector.

.foo
  .bar
    width: 10px

    &,
    ../ .baz
      height: 10px

would be rendered as

.foo .bar {
  width: 10px;
}
.foo .bar,
.foo .baz {
  height: 10px;
}

Relative references can be considered as shortcuts to the partial references with ranges like ^[0..-(N + 1)] where the N is the number of relative references used.

Root Reference

The / character at the start of a selector is a root reference. It references the root context and this means the selector won’t prepend the parent’s selector to it (unless you would use it with &). It is helpful when you need to write some styles both to some nested selector and to another one, not in the current scope.

textarea
input
  color #A7A7A7
  &:hover,
  /.is-hovered
    color #000

Compiles to:

textarea,
input {
  color: #a7a7a7;
}
textarea:hover,
input:hover,
.is-hovered {
  color: #000;
}

selector() bif

You can use the built-in selector() to get the current compiled selector. Could be used inside mixins for checks or other clever things.

.foo
  selector()
// => '.foo'

.foo
  &:hover
    selector()
// '.foo:hover'

This bif could also accept an optional string argument, in this case it would return the compiled selector. Note that it wouldn’t prepend the selector of the current scope in case it don’t have any & symbols.

.foo
  selector('.bar')
// => '.bar'

.foo
  selector('&:hover')
// '.foo:hover'

Multiple values for selector() bif

selector() bif can accept multiple values or a comma-separated list in order to create a nested selector structure easier.

{selector('.a', '.b', '.c, .d')}
  color: red

would be equal to the

.a
  .b
    .c,
    .d
      color: red

and would be rendered as

.a .b .c,
.a .b .d {
  color: #f00;
}

selectors() bif

This bif returns a comma-separated list of nested selectors for the current level:

.a
.b
&__c
content: selectors()

would be rendered as

.a .b__c {
content: '.a', '& .b', '&__c';
}

消除歧义

类似padding - n的表达式可能既被解释成减法运算,也可能被释义成一元负号属性。为了避免这种歧义,用括号包裹表达式:

pad(n)
margin (- n)

body
pad(5px)

编译为:

body {
margin: -5px;
}

然而,只有在函数中才会这样(因为函数同时用返回值扮演混合或回调)。

例如,下面这个就是OK的(产生与上面相同的结果):

body
  margin -5px

有Stylus无法处理的属性值?unquote()可以帮你:

filter unquote('progid:DXImageTransform.Microsoft.BasicImage(rotation=1)')

将会编译为:

filter progid:DXImageTransform.Microsoft.BasicImage(rotation=1)