nl_tokens: Checks whether the trap result is consistent with the state of the wrapped target .
pl_tokens: function ( ) { var trap = this . getTrap ( "isExtensible" ) ; if ( trap === undefined ) { // default forwarding behavior return Reflect . isExtensible ( this . target ) ; } var result = trap . call ( this . <mask> , this . target ) ; result = ! ! result ; // coerce to Boolean var state = Object_isExtensible ( this . target ) ; if ( result !== state ) { if ( result ) { throw new TypeError ( "cannot report non-extensible object as extensible: " + this . target ) ; } else { throw new TypeError ( "cannot report extensible object as non-extensible: " + this . target ) ; } } return state ; }