This read-only variable will return whether WebGL is enabled (true) or not (false) for your game. It will only work for those games running through a browser (ie: HTML5), and for all other platforms it will return true.
webgl_enabled
Boolean
if webgl_enabled global.quality = 1 else global.quality = 0;
The above code checks the WebGL flag and then sets the global variable "quality" accordingly.