ES6 generator lesson

gengen.js

var genGen = function(arr, loop){
  return (function* (){
    var idx = 0;
    var len = arr.length
    while(true){
      if (len === idx && loop) idx = 0;
      yield arr[idx++];
    }
  })();
};

var arr  = ["一","二","三","四","五"],
    loop = true
    ;

var kanji = genGen(arr, loop);

kanji.next().value; // => "一"
kanji.next().value; // => "二"
kanji.next().value; // => "三"
kanji.next().value; // => "四"
kanji.next().value; // => "五"

// if loop is true
// kanji.next().value; // => "一"
// else
// kanji.next().value; // => undefined