> Web browsing: Certain complex web technologies, like just-in-time (JIT) JavaScript compilation, are disabled unless the user excludes a trusted site from Lockdown Mode.
That's very cool actually. You can keep JS enabled but choose to make it run more slowly in exchange for better sandboxing
I originally understood this to mean JS was disabled entirely in safari when enabled unless a site is allowlisted. Does this mean the web will run JS “normally” but slower? Does the speed of modern phones mean a slower style of JS processing might be less discernible?
That's my interpretation. Modern JS engines have multiple tiers of optimization, which they apply in different ways based on how "hot" a piece of JavaScript is. JIT is the highest level of optimization, but also means generating and executing native code on the fly, which I assume leaves the door open for worse exploits if there's a bug in the engine. This is in contrast with bytecode interpretation, which is slower but available.
That's very cool actually. You can keep JS enabled but choose to make it run more slowly in exchange for better sandboxing