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javascript関数ドリル 初級編takeRight関数の実相のアウトプット

Posted at

##takeRight関数の課題内容
   ↓
https://js-drills.com/blog/takeright/

##take関数の取り組む前の状態
takeの逆なので簡単だと思っていた

##take関数に取り組んだ後の状態

  • (1 + i)ここの部分の理解が少し追いつかなかったです。

##tail関数の実装コード(答えを見る前)
実行できなかった

##tail関数の実装コード(答えを見た後)

function takeRight(array, n = 1) {
  if(n === 0) {
    return [];
  }
  if(n > array.length) {
    return [...array];
  }

  const takenArray = [];
  for(let i = 0; i < n; i++) {
    // array [1, 2, 3]
    // 1 + i => 1, 2, 3
    // array.length =>
    //   3 - (1 + 0) = 2,
    //   3 - (1 + 1) = 1
    //   3 - (1 + 2) = 0
    const indexFromRight = array.length - (1 + i)
    takenArray.unshift( array[indexFromRight] );
  }

  return takenArray;
}

console.log( takeRight([1, 2, 3]) );
// => [3]

console.log( takeRight([1, 2, 3], 2) );
// => [2, 3]

console.log( takeRight([1, 2, 3], 5) );
// => [1, 2, 3]

console.log( takeRight([1, 2, 3], 0) ) ;
// => []
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