Language Definitions for JSX files.

You will need to add a keyboard shortcut to tab complete in JSX files.

open up Preferences > Key Bindings - user and add this entry:

{
    "keys": ["tab"], "command": "expand_abbreviation_by_tab", "context": [
        {
            "operand": "source.js.jsx",
            "operator": "equal",
            "match_all": true,
            "key": "selector"
        },
        {
            "key": "selection_empty",
            "operator": "equal",
            "operand": true,
            "match_all": true
        }
    ]
},
{
    "keys": ["tab"], "command": "next_field", "context": [
        {
            "key": "has_next_field",
            "operator": "equal",
            "operand": true
        }
    ]
}

https://www.sublimetext.com/docs/3/scope_naming.html

JSX-SublimeText chooses to have a slim scope surface area because over naming scopes increases specificity and make it hard on color schemes.

There are 5 main areas of scope: Keywords/Support, Entities, Constants, Strings & Comments.

JSX-SublimeText opts to keep all javascript reserved words under one scope so as to distinguish between the js lanugage and the authors code.

All built-in objects and functions are placed under support.class.js and support.function.js

The entity scopes are generally assigned to the names of data structures, types and other uniquely-identifiable constructs in code and markup.

JSX-SublimeText only makes two entity assignments. First to the actual jsx/xml sections (entity.name.tag) and second to flow/ts type declarations (entity.name.type).

The line between specific/general syntax highlighting seems to be a bit of personal one. Due to my personal preference of less hilighting JSX-SublimeText is simpler than other JS/JSX syntaxes. If you find a part of the syntax is breaking your color scheme or you don't like a choice please feel free to open an issue. I'm more than happy to be told I'm wrong or convinced of a better way.

// Keywords
keyword.control.js // js reserved words
support.class.js // built-in objects
support.function.js // built-in functions

// Entities
entity.name.tag.jsx // JSX
entity.name.type // types

// Constants
constant.character.escape // escaped characters
constant.language.js // true|false|null|Infinity|NaN|undefined
constant.numeric.js // numbers
constant.character.entity.html // html character entities

// Strings
string.quoted.js
string.regexp.js

// Comments
comment.block.js // block.comments
comment.block.jsx // jsx comments
comment.line.js // line comments