myblog/node_modules/core-js/modules/$.for-of.js

var ctx         = require('./$.ctx')
  , call        = require('./$.iter-call')
  , isArrayIter = require('./$.is-array-iter')
  , anObject    = require('./$.an-object')
  , toLength    = require('./$.to-length')
  , getIterFn   = require('./core.get-iterator-method');
module.exports = function(iterable, entries, fn, that){
  var iterFn = getIterFn(iterable)
    , f      = ctx(fn, that, entries ? 2 : 1)
    , index  = 0
    , length, step, iterator;
  if(typeof iterFn != 'function')throw TypeError(iterable + ' is not iterable!');
  // fast case for arrays with default iterator
  if(isArrayIter(iterFn))for(length = toLength(iterable.length); length > index; index++){
    entries ? f(anObject(step = iterable[index])[0], step[1]) : f(iterable[index]);
  } else for(iterator = iterFn.call(iterable); !(step = iterator.next()).done; ){
    call(iterator, f, step.value, entries);
  }
};