Adding to ben336's answer, I tested your code with my Neon Color Scheme and a few different JavaScript language definitions, including JavaScriptNext, which actually did look the best:

The scopes for the init method are interesting (all are source.js, of course) -
this.init = function(); // meta.property.js variable.other.property.js
this.init : function(); // meta.function.js meta.function.json.js entity.name.function.js
this.init : true; // meta.function.js constant.other.object.key.js string.unquoted.label.js
this.init = true; // meta.function.js meta.property.js variable.other.property.js
Since the last 3 are function scoped they should be colored bright green, but the third one has a string scope and the last one a variable.other scope, so they pick up those colorings instead.
If you'd like, I can try to finagle the theme's function scope selectors to color the last 3 consistently - just open an issue or let me know here and I'll see what I can do.