Tracking Issue: Generate and publish `npm` package of JavaScript library.

[dmsnell]

There is no official npm package for this library. There are some which package it separately. It should build an artifact that be published directly to npm.

[TheSpyder]

I'm not sure how exactly google publishes from this repo to NPM, but here are the imports I use across two files
import { Diff, DIFF_DELETE, DIFF_INSERT } from 'diff-match-patch';
import { Diff, DIFF_EQUAL, diff_match_patch } from 'diff-match-patch';

Which seems to be all of the exports from index.js in the NPM package. We also use @types/diff-match-patch, but once the NPM publishing is sorted I can probably PR shipping types within the module.

[dmsnell]

@TheSpyder are you using a fork's npm package? I believe one does exist but it's unlinked from diff-match-patch itself. Or have you created your own package?

[TheSpyder]

Oh wow, I don't think my team realised the diff-match-patch NPM package was itself a fork 🫠

I hadn't quite figured out how I wanted to deploy the fork internally yet, it makes sense now why it seemed so difficult 😂

[TheSpyder]

This might be a more interesting migration than I expected. The NPM package made some slight tweaks to the API, such as JackuB/diff-match-patch#18

And given that I use it as ESM, perhaps I'll take the ideas in JackuB/diff-match-patch#20 and PR those too at some point.

[TheSpyder]

I'm tracking through the history and it looks like the JackuB fork was inherited from a previous owner. But in the end the sum of it's changes are not very much. Comparing to before your surrogate pairs fix:
diff.patch

It replaces the global export with module exports:

module.exports = diff_match_patch;
module.exports['diff_match_patch'] = diff_match_patch;
module.exports['DIFF_DELETE'] = DIFF_DELETE;
module.exports['DIFF_INSERT'] = DIFF_INSERT;
module.exports['DIFF_EQUAL'] = DIFF_EQUAL;

And replaces the entire diff_match_patch.Diff array-like class with a simple array to support JavaScript destructuring:

diff_match_patch.Diff = function(op, text) {
  return [op, text];
};

I think these are very sensible changes, I'll include them in a PR to add the other NPM package boilerplate unless you have strong opposition.