Use Normal Negative Currency

[jlind]

The MooTools formatCurrency uses a non-standard negative/prefix combination.

expect((-2000).formatCurrency()).toEqual('$ -2,000.00');

In MooTools the currency prefix is in front of the negative prefix. So currency is formatted like $ -2,000.00 and $ (2,000.00)
The standard seems to be -$2,000.00 and ($2,000.00)

Swapping the prefix ordering means it probably would break everything else... so more custom logic just for Currency? Seems like overkill.

--- Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/9195794-use-normal-negative-currency?utm_campaign=plugin&utm_content=tracker%2F22069&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F22069&utm_medium=issues&utm_source=github).

[boppy]

It seems to be a small step to make that happen. You can reformat, but the manually set pre- and suffixes are not exclusively assigned.

First things first:
Your $ (1337.42) idea is already possible. Just:

Locale.define('en-US', 'Number', {
	currency: {
		prefix: '$ ',
		negative: {
			prefix: '(',
			suffix: ')'
		}
	}
});

But it will get harder if -$ 1337.42 should be possible. But:

Locale.define('te-st').inherit('EU', 'Number');
Locale.define('te-st', 'Number',  {
	currency: {
		prefix: '€ ',
		suffix: '+',
		negative: {
			exclusive: true, // to be implemented ;)
			prefix: '-Eur ',
			suffix: '-'
		}
	}
});
Locale.use('te-st');

(-1337.42).formatCurrency();
// will output:
// € -Eur 1.337,42+-

So just change https://github.com/mootools/mootools-more/blob/master/Source/Types/Number.Format.js#L35 to:

if (negativeLocale[key] != null) options[key] = (negativeLocale.exclusive ? '' : getOption(key)) + negativeLocale[key];

The != null check is to unset a suffix set by the "root"-Number by providing ''.

With this fix, it will output -Eur 1.337,42- as expected.

See: https://jsfiddle.net/nc7fu62j/2/
It's only JS-line 22 chat has a change.

Review at https://github.com/boppy/mootools-more/tree/fix-currency-bug-1300
I will provide a PR w/ specs if you're okay with that...