nl_tokens: The iterate trap should return an iterator object .
pl_tokens: function ( ) { var trap = this . getTrap ( "iterate" ) ; if ( trap === undefined ) { // default forwarding behavior return Reflect . iterate ( this . target ) ; } var trapResult = trap . call ( this . handler , this . target ) ; if ( <mask> ( trapResult ) !== trapResult ) { throw new TypeError ( "iterate trap should return an iterator object, " + "got: " + trapResult ) ; } return trapResult ; }