How does a JavaScript engine choose what to execute next? -

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while syntactically proficient @ javascript, clueless goes on under hood. running when , how javascript engine schedules it, if indeed it's scheduled in sense of word. clueless don't know terminology should use research it.

i have assumed, hearing others parrot it, javascript engines can run 1 thread @ time. assuming true , function running when callback occurs, happens behind scenes? running function paused , callback executed or full stack of running function unwound, code in callback run.

i clueless , shameful...

how fit in ui thread in browser, how different in node.js

sorry if question bit open ended, in end asking boils down -- should research(i.e google) learn more of this.

the function being executed finishes execution before callback run. can implemented in different ways different engines.

node not different , engine responsible executing javascript code shared browsers.

since can't run 2 or more functions @ same time, , 1 function needs finish execution before other gets executed, javascript said single threaded.

web workers run on separate environment, execution not dependent on code running in page or other web workers.


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