Download JS Blocker (JSB5.safariextz, 504 KB)
Double-click file to install or drag onto Safari icon. If you receive an error while installing, you may have to uninstall your current version first. Create a backup before doing so by opening the Settings menu in the JSB popover and then choose Backup. Be sure to include everything in the backup. You can now safely uninstall your current version. If your settings are gone when you install the new version, just import the backup you exported earlier.
SHA1 hash: 036a3f8344d9eebbf59c155e28db02d34a5b50ac
JS Blocker downloaded from outside the Safari Extension Gallery will cease to function in Safari 12 and macOS Mojave (10.14). Developer-signed Safari extensions are not supported in Safari 12. Safari extensions distributed in the Safari Extension Gallery are deprecated, and Safari 12 is the last release to support them.
Safari App Extension
I have no experience creating native mac apps; it will therefore be impossible for me to re-create JSB as one.
Users who downloaded JS Blocker from the Safari Extension Gallery will probably not be able to update beyond 5.2.2. Apple is not responding to my requests for updates despite them saying they will accept submissions until the end of 2018.