alt Hacker NewsBDHS seems strictly less powerful than a time travel debugger. You can just set a hardware breakpoint and run backwards until the value is set.
Why not just do proper time travel? Is that absent for Javascript?
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acemarke • last Thursday at 4:33 PM
We actually built a full-blown time travel debugger for Javascript at Replay.io:
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Good point - in theory a full time-travel debugger is more powerful. The practical limitation is that time-travel for JavaScript usually requires instrumenting the code or running inside a custom record/replay environment. Today, JavaScript doesn’t expose any record/replay mechanism, access to hardware breakpoints, or the internal VM state needed to run execution backwards.
The browser’s debugging API (CDP) also doesn’t provide a way to capture or rewind engine state without modifying the application.
BDHS works within the constraints of zero instrumentation: it relies only on Debugger.paused and heap snapshots, so it can trace where a value originates without altering the code being debugged.