nl_tokens: One of a known set of options
pl_tokens: function SelectionType ( typeSpec ) { if ( ! Array . isArray ( typeSpec . data ) && typeof typeSpec . data !== 'function' ) { throw new Error ( 'instances of SelectionType need typeSpec.data to be an array or function that returns an array:' + JSON . stringify ( typeSpec ) ) ; } Object . keys ( typeSpec ) . forEach ( function ( <mask> ) { this [ key ] = typeSpec [ key ] ; } , this ) ; }