Sublime Text 3 doesn't highlight some JavaScript object properties.
Screenshot:
Hopefully, the picture is pretty much self-explaining. Why doesn't my "this.description" property get the proper syntax highlight?
The syntax package is only part of the equation, the other is the color scheme. Different color schemes highlight code differently, even with the same syntax package in use. You seem to be using a variant of the Monokai scheme, but I cannot reproduce your issue with the bundled version of Monokai.
In general I recommend using Babel over the default JavaScript packagesince it supports ES6+ and JSX. Maybe that alone solves your problem, otherwise try a different color scheme.