How does this code work? #32

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1. ivanff commented on Apr 28, 2023

   

   ivanff

   on Apr 28, 2023

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   yes, it still works, thanks to Ruslan
2. saurav-codes commented on Sep 14, 2024

   

   saurav-codes

   on Sep 14, 2024

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   i also want to understand how does it works? do we simply link the script before timer script.?
3. turuslan commented on Sep 18, 2024

   

   turuslan

   on Sep 18, 2024

   Owner

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   Hello.
   Sorry for late comment.

   Scripts may create frequent timers

   window.setInterval(action, 10ms)
   

   Frequent timers consume more battery
   (also these timers can be used for annoying things like ads)
   so browsers throttle window timers (reduce frequency, increase delay)
   when tab or windows becomes background.

   action() after 10ms
   action() after 10ms
   action() after 10ms
   // tab becomes background
   action() after 1000ms
   action() after 1000ms
   ...
   

   Although window.setInterval is slowed down,
   but there seems to be several techniques that work around that.

   One of them is using Worker.
   Worker is created on separate thread from window's ui thread.
   Seems that browsers don't throttle Worker timers.
   Worker can postMessage to window,
   which calls window.onmessage.
   Seems that browsers don't throttle window.onmessage too.

   This library overwrites window.setInterval function
   and forwards setInterval call to Worker via worker.postMessage,
   remembering original window callback.
   Worker calls self.setInterval and worker callback
   calls self.postMessage to wake window.onmessage,
   which calls original window callback.

   flowchart TB
       subgraph window
           a1("window.setInterval(action)")
           a2("worker.postMessage()")
           a6("worker.onmessage")
           a7("action")
       end
       subgraph worker
           a3("self.onmessage")
           a4("self.setInterval()")
           a5("self.postMessage()")
       end
       a1-->a2-->a3-->a4-->a5-->a6-->a7
       a1-. "action()" .->a6
   

   Loading

   Library script hacktimer.js overwrites window.setInterval.
   It must execute before any other script.
   If some other script will execute before,
   it will call slow window.setInterval version.

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