random-with-units.md.erb

---
title: "Breaking Change: Random With Units"
introduction: >
  The `random()` function will no longer ignore units on the `$limit` argument
  in a future version. Passing a `$limit` with units is deprecated to ensure the
  compilation results don't change once the new behavior lands.
---

[The `random()` function] has historically ignored units in `$limit` and
returned a unitless value. For example `random(100px)` would drop "px" and
return a value like `42`.

A future implementation of Dart Sass will stop ignoring units for the `$limit`
argument and return a random integer with the same units.

[The `random()` function]: ../modules/math#random

<% example(autogen_css: false) do %>
  // Future Sass, doesn't work yet!
  @debug math.random(100px); // 42px
  ===
  // Future Sass, doesn't work yet!
  @debug math.random(100px)  // 42px
<% end %>

## Transition Period

<% impl_status dart: '1.54.5', libsass: false, ruby: false %>

First, the Sass compiler will emit a deprecation warning for previous uses of
`random()` when the `$limit` argument has units. The warning will suggest a way
to preserve the existing behavior and another way that emulates the future
implementation.

In Dart 2.0.0 passing a `$limit` number with units will be an error, and then in
a future minor release the `random()` function will return a random integer the
same units as `$limit`.