javascript - 用 `for` 循环替换 `forEach` 循环

Question

我正在研究将任务卡移至下一列的 StateService 方法。我能够编写工作正常的 taskMoveLeft 方法，但我无法使用 forEach 循环为 taskMoveRight 方法复制它的功能，我可以让它只与 for 循环一起工作。

taskMoveLeft 方法的工作示例(使用 forEach):

taskMoveLeft(id) {
  state.columns.forEach((column, columnIndex) => {
    if (state.columns[0] !== column) {
      if (column.cards) {
        column.cards.forEach((card, cardIndex) => {
          if (card.id === id) {
            if (state.columns[columnIndex - 1].cards) {
              // Add card to the target column card collection
              state.columns[columnIndex - 1].cards.push(card);
            } else {
              // Create target column card collection and add card
              state.columns[columnIndex - 1].cards = Array.of();
              state.columns[columnIndex - 1].cards.push(card);
            }
            // Remove the card from the source column card collecion
            state.columns[columnIndex].cards.splice(cardIndex, 1);
          }
        });
      }
    }
  });
}

taskMoveRight 方法的工作示例(使用 for 循环):

taskMoveRight(id) {
  for (let i = 0; i < state.columns.length; i++) {
    if (state.columns[state.columns.length - 1] !== state.columns[i]) {
      if (state.columns[i].cards) {
        for (let j = 0; j < state.columns[i].cards.length; j++) {
          if (state.columns[i].cards[j].id === id) {
            if (state.columns[i + 1].cards) {
              // Add card to the target column card collection
              state.columns[i + 1].cards.push(state.columns[i].cards[j]);
            } else {
              // Create target column card collection and add card
              state.columns[i + 1].cards = Array.of();
              state.columns[i + 1].cards.push(state.columns[i].cards[j]);
            }
            // Remove the card from the source column card collecion
            return state.columns[i].cards.splice(j, 1);
          }
        }
      }
    }
  }
}

无法使 taskMoveRight 方法与 forEach 循环一起使用。使用此代码，卡片总是移动到最右边的列:

taskMoveRight(id) {
  state.columns.forEach((column, columnIndex) => {
    if (state.columns[state.columns.length - 1] !== column) {
      if (column.cards) {
        column.cards.forEach((card, cardIndex) => {
          if (card.id === id) {
            // Create target column card collection
            if (!state.columns[columnIndex + 1].cards) {
              state.columns[columnIndex + 1].cards = Array.of();
            }
            // Add card to the target column card collection
            state.columns[columnIndex + 1].cards.push(card);
            // Remove the card from the source column card collecion
            state.columns[columnIndex].cards.splice(cardIndex, 1);
          }
        });
      }
    }
  });
}

Answer 1

forEach 不是合适的工具，因为您提前终止了循环。相反，由于您需要卡片的索引，请使用 findIndex。请参阅 *** 评论和其他建议:

taskMoveRight(id) {
  for (let i = 0; i < state.columns.length; i++) {
    // *** Instead of repeating it all over
    const column = state.columns[i];
    if (state.columns[state.columns.length - 1] !== column) {
      if (column.cards) {
        // *** Find the card
        const cardIndex = column.cards.findIndex(card => card.id == id);
        // *** Get the card if found
        const card = cardIndex !== -1 && column.cards[cardIndex];
        if (card) {
            // *** Instead of repeating it
            const nextColumn = state.columns[i + 1];
            if (nextColumn.cards) {
              // Add card to the target column card collection
              nextColumn.cards.push(card);
            } else {
              // Create target column card collection and add card
              // *** Using Array.of() to create an empty array and then pushing
              // *** to it is quite round-about; instead: [card]
              nextColumn.cards = [card];
            }
            // Remove the card from the source column card collecion
            return column.cards.splice(cardIndex, 1);
        }
      }
    }
  }
}