Refactor document and add explaining comment
Add failing test
Whitelist characters to unescape
Test only 1 thing per test

i.e. Don’t test curly-brackets in test for optional syntax
Only unescape ampersand characters

With current parser, curly brackets and spaces aren’t being escaped.
Test for both html entities in javascript that can cause syntax errors
Use single quote instead of escaping double quotes
Simplify `to_s` comment
Rename method

Much clearer
Remove unnecessary comments
Merge branch 'fix-html-entity-escaping'