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.