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[クイズ]javascriptと仲良くなるための一歩　第３８話「配列」

Posted at 2017-08-24

問題

var arr = [0,,2]
arr[1] //=> ?

var arr = [0]
arr[2] = 2
arr[1]     //=> ?
arr.length //=> ?

var arr = [0,,2]
arr[1] //=> undefined

var arr = [0]
arr[2] = 2
arr[1]     //=> undefined
arr.length //=> 3