Interpolation

Stylus supports interpolation by using the {} characters to surround an expression, which then becomes part of the identifier. For example, -webkit-{'border' + '-radius'} evaluates to -webkit-border-radius.

A great example use-case for this is expanding properties with vendor prefixes.

  vendor(prop, args)
    -webkit-{prop} args
    -moz-{prop} args
    {prop} args

  border-radius()
    vendor('border-radius', arguments)
  
  box-shadow()
    vendor('box-shadow', arguments)

  button
    border-radius 1px 2px / 3px 4px

Yields:

  button {
    -webkit-border-radius: 1px 2px / 3px 4px;
    -moz-border-radius: 1px 2px / 3px 4px;
    border-radius: 1px 2px / 3px 4px;
  }

Selector Interpolation

Interpolation works with selectors as well. For example, we may iterate to assign the height property for the first 5 rows in a table, as shown below:

table
  for row in 1 2 3 4 5
    tr:nth-child({row})
      height: 10px * row

Yields:

table tr:nth-child(1) {
  height: 10px;
}
table tr:nth-child(2) {
  height: 20px;
}
table tr:nth-child(3) {
  height: 30px;
}
table tr:nth-child(4) {
  height: 40px;
}
table tr:nth-child(5) {
  height: 50px;
}

You may also put together multiple selectors into one variable by building a string and interpolate them in place:

mySelectors = '#foo,#bar,.baz'

{mySelectors}
  background: #000

Yields:

#foo,
#bar,
.baz {
  background: #000;
}