[JSCodeGen] "LET" keyword

[Toky Olivier Razanakotonarivo]

Hello, can you implement please “LET” keyword? at least for JSCodeGen?

As you can see here: https://stackoverflow.com/questions/11488014/asynchronous-process-inside-a-javascript-for-loop

VAR doesn’t work in an event loop of the form

for var i:=0 to 5 do begin
  asynchrounousTask(procedure () 
  begin
    print(i); //it will be written "6" always.
  end);
end;

Is it possible to add also “forEach” helper with arrays?

var arr: array of int;
arr.forEach(procedure(i: int)
begin
  print (i);
end);

Thank you Eric.

[Eric Grange]

As an alternative, the codegen could be adapted to use “let” instead of “var” for loop variables. This would diverge from Delphi’s capture mechanism, but be more inline with expectations.

Generally speaking “let” could be leveraged throughout the codegen to simplify scoping, as JS’s “let” is closer to Pascal’s “var” most of the time, the exception being capture of loop variables.

caniuse indicates to 96% support for “let”, so it should be safe to migrate the codegen

Supporting forEach should already be possible through helpers.

[Toky Olivier Razanakotonarivo]

OK thank you Eric!

[Toky Olivier Razanakotonarivo]

Hello, any news for this request please? Thank you

[Eric Grange]

Not as straightforward as I first thought, as the loop var is currently declared outside of the “for” expression in the AST, so the codegen will need extra hinting so it won’t declare the variable outside of the loop.

[Toky Olivier Razanakotonarivo]

Okay, thank you. So I need to find another method.