classify glyphset

[jimmywarting]

Description

Motivation and Context

part of #247 as a modernization

How Has This Been Tested?

npm run test

Screenshots (if appropriate):

Types of changes

• Refactor to modern code (no behaviour changes)

Checklist:

• I did npm run test and all tests passed green (including code styling checks).
• I have added tests to cover my changes.
• My change requires a change to the documentation.
• I have updated the README accordingly.
• I have read the CONTRIBUTING document.

[ILOVEPIE]

@Connum The question is though, do we want to switch to classes? This breaks compatibility with legacy browsers, especially in the standalone non-npm versions of opentype.js. Some applications may depend on opentype.js for polyfilling webfonts in legacy browsers, which means that we'd be breaking those polyfills. Maybe there's a compiler pass we could apply to convert from classes to functions or from classes to Object.create when compiling non-npm versions?

[ILOVEPIE]

As long as we can keep it ES5 compatable I don't see an issue, but we need to make sure we can do that.

[Connum]

Doesn't rollup with the buble and commonjs plugins make sure that everything's compiled the way we need it to? I haven't used rollup in myself projects before and haven't looked into it more deeply yet, but that's what I understood from a quick glance at it.