動的な配列って何？ - Qiita

let fileIndex = [1,2,3,4,5,6,7,8,9,10]; fileIndex.shift(); console.log(fileIndex); //9[2,3,4,5,6,7,8,9,10] fileIndex.push(fileIndex[fileIndex.length - 1] + 1) //計算の順番に並べてます //fileIndex.push(fileIndex[9 - 1] + 1) //fileIndex.push(fileIndex[8] + 1) //2,3,4,5,6,7,8,9,10 ←この数字を取り出す //0,1,2,3,4,5,6,7,[8番目] 配列の順番は下の文になります。 //↓そのために //10 //fileIndex.push(10 + 1) //fileIndex.push(11) consol.log(fileIndex)