Does the right thing: javascript off by default, enabled per-site.

A nice simple add-on that does exactly what I want, which is block Javascript based on the site by default, but it allows me to turn it on for any site with a simple click. And it works in Firefox 57, which is nice, because at the time of writing, NoScript doesn't support Firefox 57.

The ''default policy'' IS correct. Having it in reverse is a security risk, nullifies using the addon in first place and makes it pointless.

"so that users may choose to block nothing until they encounter a problem site (and then block JS if they want)."
- and by then it would be too late. My comment was spot on and needed to stop the useless spamming. The addon you want is noscript (or none at all).