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The explicitness is the reason currently you can assume* that if nobody will ever modify variables unless you explicitly give up control somehow, if you were to

by cwmma 10y ago

The explicitness is the reason currently you can assume* that if nobody will ever modify variables unless you explicitly give up control somehow, if you were to have implicit await then that would no longer be the case and any function call could theoretically pause the function and give up control to other functions. *certain DOM APIs due violate this contract, notably window.open() on firefox pauses everything but setTimeout.

gpderetta 10y ago
The problem with that is that any mutable escaped variable (i.e. explicitly or implicitly global) can be potentially modified by any function call. On the other hand a non escaped variable cannot be mutated behind your back, yield or no yield. At least, that's the case in a sane language, not sure about JS.
- cwmma 10y ago
  escaped/non-escaped variables are not a thing in JS
  - gpderetta 10y ago
    There are no locals in JS (honest question)? If that the case you have to assume that everything can be mutated everywhere unless for those functions that explicitly and fully document their side effects (and yield would certainly be a side effect).
    - cwmma 10y ago
      variables declared with the var keyword are functionally scoped in JS so they are local to the function they are declared in and are lexically scoped to the closure of that function. So your local variables you can be fairly confident are not mutated anywhere else. That being said you can totally have globals and whatnot that can be mutated anywhere (e.g. parameters passed to a function or literal globals installed in the global scope) or things declared at a lower scope that can still be modified by multiple functions. Hope that clears it up
olau 10y ago
Just to expand a bit upon this: That you can assume a single thread simplifies the code immensely, e.g. when modifying state. It's important to be explicit about when this assumption is broken.

by cwmma 10y ago

gpderetta 10y ago

The problem with that is that any mutable escaped variable (i.e. explicitly or implicitly global) can be potentially modified by any function call. On the other hand a non escaped variable cannot be mutated behind your back, yield or no yield. At least, that's the case in a sane language, not sure about JS.

cwmma 10y ago
escaped/non-escaped variables are not a thing in JS
- gpderetta 10y ago
  There are no locals in JS (honest question)? If that the case you have to assume that everything can be mutated everywhere unless for those functions that explicitly and fully document their side effects (and yield would certainly be a side effect).
  - cwmma 10y ago
    variables declared with the var keyword are functionally scoped in JS so they are local to the function they are declared in and are lexically scoped to the closure of that function. So your local variables you can be fairly confident are not mutated anywhere else. That being said you can totally have globals and whatnot that can be mutated anywhere (e.g. parameters passed to a function or literal globals installed in the global scope) or things declared at a lower scope that can still be modified by multiple functions. Hope that clears it up

olau 10y ago

Just to expand a bit upon this: That you can assume a single thread simplifies the code immensely, e.g. when modifying state. It's important to be explicit about when this assumption is broken.