Get a setting value conditionally in the Customizer api

I’m not sure if this is what you wanted, but you can use wp.customize.get() to get all the currently set Customizer settings:

var settings = wp.customize.get(); // get all settings
var border_style = settings['myplugin[border_style]'];
var border_color = settings['myplugin[border_color]'];

// Or, this works, too.
var border_style = wp.customize.get()['myplugin[border_style]'];
var border_color = wp.customize.get()['myplugin[border_color]'];

Reference