No more vars in JavaScript docs

[wbamberg]

After the Write the Docs sprint, these are all the pages in the JavaScript documentation that use var, according to my very basic script:

• https://developer.mozilla.org/en-US/docs/web/javascript/guide/grammar_and_types
• https://developer.mozilla.org/en-US/docs/web/javascript/guide/control_flow_and_error_handling
• https://developer.mozilla.org/en-US/docs/web/javascript/guide/functions
• https://developer.mozilla.org/en-US/docs/web/javascript/the_performance_hazards_of_prototype_mutation
• https://developer.mozilla.org/en-US/docs/web/javascript/memory_management
• https://developer.mozilla.org/en-US/docs/web/javascript/enumerability_and_ownership_of_properties
• https://developer.mozilla.org/en-US/docs/web/javascript/closures
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/delete
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/await
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/new
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/this
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/comma_operator
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/operators/typeof
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/classes/extends
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/classes/class_static_initialization_blocks
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/deprecated_and_obsolete_features/the_legacy_iterator_protocol
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/var
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/throw
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/const
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/let
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/for
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/function_star_
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/break
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/block
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/array/from
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/array/@@iterator
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/typedarray/findindex
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/typedarray/values
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/cosh
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/clz32
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/asinh
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/imul
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/tanh
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/sinh
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/math/hypot
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/memory
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/memory/memory
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/memory/buffer
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/module/exports
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/table/get
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/webassembly/instantiate
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/object/entries
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/object/defineproperties
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/object/keys
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/object/setprototypeof
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/string/repeat
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/string/trimstart
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/string/codepointat
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/string/fromcodepoint
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/global_objects/string/startswith
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/strict_mode
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/strict_mode/transitioning_to_strict_mode
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/functions
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/functions/default_parameters
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/functions/arrow_functions
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/functions/arguments
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/functions/arguments/callee
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/deprecated_string_generics
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/not_defined
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/stmt_after_return
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/undeclared_var
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/cant_access_lexical_declaration_before_init
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/getter_only
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/not_a_function
• https://developer.mozilla.org/en-US/docs/web/javascript/reference/errors/is_not_iterable

There are likely to be some false positives in there. Note that we should not change any code inside polyfills.

[Abhiram-Gullapalli]

I want to take up this issue.
Just for confirmation, the issue is about changing the var variable to the alternative one for the necessary context.

[wbamberg]

I want to take up this issue. Just for confirmation, the issue is about changing the var variable to the alternative one for the necessary context.

Thank you @gullapalli9482 ! Yes (sorry I should have provided more context) exactly, this is about replacing usages of var with let or const as appropriate.

Note that our policy here is "use const where we can, let where we have to", and that we are not updating usages inside polyfills.

I don't personally mind much how many files you include in each PR, but I do recommend if possible that you include at least a few in each PR, rather than one PR per page.

[Abhiram-Gullapalli]

Definitely 👍🏼 .

[ghost]

I'm going to try clearing up any var from all of the WebAssembly documentation soon, but immediately, I'm starting with the examples repository, as most examples are copy-and-pasted from it, and link to it.

Note that there was a lot more than the basic search had caught.

[wbamberg]

Thanks @phosra . I'm sure there are more, yes, but any progress here is good!

[Josh-Cena]

I've done a basic run-through and removed the false-positives from polyfills (which will be removed anyway) and intended usages. Only about 35 pages left.

[Josh-Cena]

As far as I can tell this seems to be done—can we do a run-down to confirm all the remaining usages are intended?

[teoli2003]

These are the only ones with a var entry:

• reference/functions/index.md
• reference/errors/deprecated_expression_closures/index.md
• reference/errors/delete_in_strict_mode/index.md
• reference/functions/default_parameters/index.md
• reference/strict_mode/index.md
• reference/global_objects/error/index.md
• reference/global_objects/eval/index.md
• reference/statements/block/index.md
• reference/global_objects/function/call/index.md
• reference/statements/for/index.md
• reference/statements/let/index.md
• reference/statements/for...in/index.md
• reference/statements/const/index.md
• reference/global_objects/array/@@unscopables/index.md
• reference/statements/function/index.md
• reference/statements/var/index.md
• closures/index.md
• a_re-introduction_to_javascript/index.md
• reference/classes/class_static_initialization_blocks/index.md
• reference/operators/delete/index.md
• reference/operators/this/index.md
• reference/operators/function/index.md
• guide/control_flow_and_error_handling/index.md
• guide/grammar_and_types/index.md
• guide/modules/index.md
• guide/details_of_the_object_model/index.md

I'll check them and ask questions if I have any doubt. (We'll do this when I'm back later today)

[Josh-Cena]

The details_of_the_object_model needs a total revamp so I've kept it out for now (tracked in #10301). Otherwise it's quite weird to have const/let but all other syntax totally outdated.

[teoli2003]

There are other examples still, for example, I caught another in #18196

Yes, this issue is about the Web/JavaScript/ directory; we still have plenty vars to fix in Web/API, Games/, …
This is a first milestone (Yes, maintaining 10000+ pages is sometimes cumbersome).

[Josh-Cena]

@teoli2003 did you get to do the last run-down? Judging from the recent unsuccessful attempts to change more vars to consts, I'm pretty confident it's all done.

[teoli2003]

LGTM, let's close this one. \o/