var ITERATOR = require('./$.wks')('iterator') , SAFE_CLOSING = false; try { var riter = [7][ITERATOR](); riter['return'] = function(){ SAFE_CLOSING = true; }; Array.from(riter, function(){ throw 2; }); } catch(e){ /* empty */ } module.exports = function(exec, skipClosing){ if(!skipClosing && !SAFE_CLOSING)return false; var safe = false; try { var arr = [7] , iter = arr[ITERATOR](); iter.next = function(){ return {done: safe = true}; }; arr[ITERATOR] = function(){ return iter; }; exec(arr); } catch(e){ /* empty */ } return safe; };