Allow line numbers to match debug() call in browser consoles

[fijiwebdesign]

A possible starting point to fixing file and line number mapping in the browser, #198 as well as for sourcemaps with browserify and webpack, #223

I'm not sure what of the full formatting scope that is done in enabled() or if it can be integrated into this approach for matching line numbers. This approach has the limitation that it needs to do formatting up front when debug() is called. This is because debug() has to return console.log() directly. i.e: return console.log.bind(console, '%c%s +%sms', 'color: ' + self.color, namespace, interval) to preserve line numbers.

This limits to using bind() to add formatting to console.log().

Currently it supports the color formatting of namespace and ms interval. The ms interval is now directly after the namespace due to limitation that we can only prepend arguments to Function.prototype.bind().

[neojp]

👍 I wish this was merged. Thanks @fijiwebdesign

[TooTallNate]

Very clever, but as you mention it has the limitation that formatters are disabled, which is probably a no-go, or at least a major version bump.

[TooTallNate]

I think we could make something like debug('foo %s')('bar') would, where the middle function call returns the bound console.log function with the formatter appended. Would be slower for sure, and a breaking API change.

[jabaz]

This works well, but setting color manually, has no effect!

[thebigredgeek]

@jabaz can you explain?

[thebigredgeek]

#370