獲取先前的值并更新n 1項

我有一個序列陣列，我想要實作的是最后一個物件的完成屬性為真，然后下一個物件的下一個物件的is_to_happen為真

輸入

const sequences = [
    {
        "title": "Order placed",
        "completed": true
    },
    {
        "title": "To be confirmed",
        "completed": false
    },
    {
        "title": "Approx Thursday product will be shipped",
        "completed": false
    }
]

這就是我想要的預期輸出

const output = [
    {
        "title": "Order placed",
        "completed": true,
        "is_to_happen": false
    },
    {
        "title": "To be confirmed",
        "completed": false,
        "is_to_happen": false
    },
    {
        "title": "Approx Thursday product will be shipped",
        "completed": false,
        "is_to_happen": true
    }
]

到目前為止我嘗試使用 array.reduce 的方法不起作用

sequences.reduce((acc,curr) => {
    acc = [...acc, curr]
    if(curr.completed){
     acc = [...acc, {...curr, is_to_happen: true}]
    }
    return acc     
}, [])

uj5u.com熱心網友回復：

Usea reduce，并跟蹤completed專案的索引：

const sequences = [
    {
        "title": "Order placed",
        "completed": true
    },
    {
        "title": "To be confirmed",
        "completed": false
    },
    {
        "title": "Approx Thursday product will be shipped",
        "completed": false
    },
    { "title": "One more step", "completed": false }
]

const result = sequences.reduce ( (acc,item, i) => {
  if(item.completed) acc.completedIndex = i;
  acc.items.push( {...item,"is_to_happen": (acc.completedIndex != -1) && (i >= acc.completedIndex 2) } );
  return acc;
},{items:[], completedIndex:-1});

console.log(result.items);

實作相同目的的另一種方法是向后查看completed標志的原始陣列中的 2 個元素

const sequences = [
    {
        "title": "Order placed",
        "completed": true
    },
    {
        "title": "To be confirmed",
        "completed": false
    },
    {
        "title": "Approx Thursday product will be shipped",
        "completed": false
    }
]

const result = sequences.map ( (item, i) => {
  return {...item, is_to_happen: !!sequences[i-2]?.completed};
});

console.log(result);

uj5u.com熱心網友回復：

這是一種方法：

 const todo = [
        {
            "title": "Order placed",
            "completed": true
        },
        {
            "title": "To be confirmed",
            "completed": false
        },
        {
            "title": "Approx Thursday product will be shipped",
            "completed": false
        }
    ]
    
    // find last completed
    var lastCompleted = todo.slice().reverse().find(item => item.completed === true);
    // get the index of the next to the next item.
    var nextToDoIndex = todo.indexOf(lastCompleted)   2;
    // only change it if it exists.
    if(todo[nextToDoIndex]) todo[nextToDoIndex] = {...todo[nextToDoIndex], is_to_happen: true } 

    console.log(todo)

uj5u.com熱心網友回復：

sequences.reduce((acc, curr) => {
  if (curr.completed)
    acc = [...acc, { ...curr, is_to_happen: true }]
  else
    acc = [...acc, { ...curr, is_to_happen: false }]
  return acc
}, [])

嘗試這個。

uj5u.com熱心網友回復：

sequences.reduce((acc, curr, i, arr) => {
  if (i === arr.length-1)
    acc = [...acc, { ...curr, is_to_happen: true }]
  else
    acc = [...acc, { ...curr, is_to_happen: false }]
  return acc
}, [])

嘗試這個。

標籤：javascript

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