freifunk-app/node_modules/core-js/library/modules/$.iter-detect.js

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;
};