Less 的Each用法

Each函数是Less v3.7版本的新增用法，用于批量生成模板样式。
文档如下：

each Released v3.7.0

Bind the evaluation of a ruleset to each member of a list.c
把规则的计算绑定到列表的每一个成员身上
Example:
例如：

@selectors: blue, green, red;

each(@selectors, {
  .sel-@{value} {
    a: b;
  }
});

Outputs:
输出：

.sel-blue {
  a: b;
}
.sel-green {
  a: b;
}
.sel-red {
  a: b;
}

By default, each ruleset is bound, per list member, to a @value, @key, and @index variable. For most lists, @key and @index will be assigned the same value (numerical position, 1-based). However, you can also use rulesets themselves as structured lists. As in:
每个列表成员可以被默认绑定@value,@key,@index三个变量，对大部分的列表而言， @key和 @index会被定义为相同的值（比如以1开始的有序列表）。然而，你也可以使用规则自定义列表中的@key值

@set: {
  one: blue;
  two: green;
  three: red;
}
.set {
  each(@set, {
    @{key}-@{index}: @value;
  });
}

This will output:
输出结果：

.set {
  one-1: blue;
  two-2: green;
  three-3: red;
}

Since you can, of course, call mixins with guards for each ruleset call, this makes each() a very powerful function.
因此你可以混合为每个each规则设定它的参数，这样会让each()函数成为一个非常有用的函数

Setting variable names in each()

在each()中设置变量名

You don't have to use @value, @key, and @index in your each() function. In Less 3.7, with the each() function, Less is introducing the concept of anonymous mixins, which may expand to other parts of the syntax at a later date.
在 每个each()函数中你不必都使用@value,@key,@index作为变量名。在Less 3.7版本中，因为each()函数， Less被描述为可以接受匿名不定参数，这一特性将会扩展到其他的语法中
An anonymous mixin uses the form of #() or .() starting with . or # just like a regular mixin would. In each(), you can use it like this:
一个匿名不定参数可以用#()或者 .()的样式为开头

.set-2() {
  one: blue;
  two: green;
  three: red;
}
.set-2 {
  // Call mixin and iterate each rule
  each(.set-2(), .(@v, @k, @i) {
    @{k}-@{i}: @v;
  });
}

This outputs, as expected:
输出：

.set-2 {
  one-1: blue;
  two-2: green;
  three-3: red;
}

The each() function will take the variable names defined in the anonymous mixin and bind them to the @value, @key and @index values, in that order. If you only write each(@list, #(@value) {}), then neither @key nor @index will be defined.
each()函数会获取不定参数中的变量的名字并按顺序把它们赋给到@value、@key、@index的value值。如果你只是写了each(@list, #(@value){}), name@key和@value都不会被定义