JavascriptのString#split console.log("".split(",")); undefinedかと思いきや，要素""のみの配列 console.log("a".split(",")); "a"のみ console.log("a,b,c".split(",")); "a", "b", "c"の3個 "a,b,".split(",") 試していない．"a", "b", ""の3個だと思う…