Console.log CSS should support initial (or unset/revert)

[0az]

When pretty-printing output, it's common to apply a style for a span, before reverting back to the terminal's default style. This is used in terminal prompts and in log output, for example.

As a specific motivating example, consider this output (this program does not output color to non-tty stdouts).

; deno run --allow-env --allow-net --allow-hrtime src/index.ts | cat
Check file:///[snipped]/src/index.ts
Listening on port 8000
status=200 route="POST /" duration=1.3ms
status=200 route="GET /" duration=0.3ms
status=200 route="PUT /" duration=0.2ms
status=200 route="DELETE /" duration=0.2ms
status=200 route="HEAD /" duration=0.1ms

With color, it looks like this:

But what if we want to use background-color instead?

In this case, I simply forgot to change the color: white used as resets to background-color: black. That's an easy fix, but it shows the limitations of the current level of support. Furthermore, this color reset is fragile. What if the user uses a green terminal background?

This breaks in an ugly way.

A quick test reveals that support exists in Firefox:

console.log('%cRED%cUNSET', 'color: red', 'color: unset')

Thus, implementing at least one of initial/unset/revert is needed to make it easier to write good programs with well-formatted console output, in addition to improving parity with web platforms.