Try accessing the array this.runtime.all_global_vars. It is a list of all global cr.eventvariable objects. You can learn more by browsing the source, but the important members of an event variable are:
ev.name // variable name
ev.vartype // the variable type, 0 = number, 1 = string
ev.data // the value
You can use this to look up and retrieve global variables by name, but note if you change a value, you *must* respect the vartype member, else you will break the runtime. (i.e. don't set 'data' to a number if vartype indicates it's a string.)
Edit: moving to Javascript SDK forum.