defaultOptions for js

[zilioti]

Hi @bitwiseman,
since I worked in the tests for options core in #1446, I decided to take a chance at doing #1364.

I opened this PR with the basic idea to check if the below implementation is desired by @tkrotoff:

import { html_beautify } from 'js-beautify';

const excludeButton = html_beautify.defaultOptions.unformatted.filter(tag => tag !== 'button');
const niceHtml = html_beautify(uglyHtml, { unformatted: excludeButton });

Also, could you guide me where should I test? I made just a basic one for now.

[bitwiseman]

@zilioti
The defaultOptions should probably be functions that return new instances of each Options when called. Otherwise someone could change the defaultOptions and side-effect unexpectedly.

Other than that this seems great.

[bitwiseman]

@zilioti
Also this will need be exposed via the legacy packages.

[zilioti]

Hi @bitwiseman,

I changed the defaultOptions to be a function.
Regarding the legacy packages, I think that was already done. I added a test to check it 😄!

[bitwiseman]

This addresses the issue as filed.
I'll open a new issue to add a defaultOptions to the main beautifier object in js/src/index.js that gives a cleaned up default options object.