检查对象文字数组中的重复值，并从中创建新对象

Question

我目前有任何对象文字数组，有可能使用重复值进入客户端（请参阅Date键）。

[
    {
        "Date": "2/26/2018",
        "Title": "Story 1"
    },
    {
        "Date": "2/27/2018",
        "Title": "Story 2"
    },
    {
        "Date": "2/27/2018",
        "Title": "Story 3"
    },
    {
        "Date": "2/28/2018",
        "Title": "Story 4"        
    }
]

如何检查上一个键的值以将其合并到一个新对象中，例如：

[
    {
        "Date": "2/26/2018",
        "Title": "Story 1"
    },
    {
        "Date": "2/27/2018",
        "Stories": {
            [
                {
                   "Title": "Story 2"
                },
                {
                   "Title": "Story 3"
                }
            ]
        }
    },
    {
        "Date": "2/28/2018",
        "Title": "Story 4"        
    }
]

这是踢球者 - 没有像Underscore.js这样的框架可以使用。

思考？

Answer 1

您可以使用reduce功能

var array = [    {        "Date": "2/26/2018",        "Title": "Story 1"    },    {        "Date": "2/27/2018",        "Title": "Story 2"    },    {        "Date": "2/27/2018",        "Title": "Story 3"    },    {        "Date": "2/28/2018",        "Title": "Story 4"            }];

var result = Object.values(array.reduce((a, c) => {
  if (a[c.Date]) {
    a[c.Date].Stories.push({Title: c.Title});
  } else {
    a[c.Date] = { "Date": c.Date, "Stories": [{Title: c.Title}] };
  }
  
  return a;
}, {}));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

我认为你需要更多地解决这个问题。

这与SQL中的GROUP BY语句非常相似 - 基本上，在这种情况下，您将由Date进行分组。

我会这样做：

function parseStories(stories) {
  // we're going to record previous stories in an object using their date, as that is the value we wish to group by
  var previousStories = {};
  stories.forEach(function (storyObj) {
    // this is how we should insert the object - it fits the "shape" of object retrieval where there is more than 1 result
    var insertObj = { Title: storyObj.Title };
    if (previousStories[storyObj.Date]) {
      // date already exists
      previousStories[storyObj.Date].push(insertObj);
    } else {
      // new date
      previousStories[storyObj.Date] = [insertObj];
    }
  });

  // we generate the return result
  var returnResult = [];
  // NOTE - object property order is not guaranteed; however, you can mitigate this by using an array to sort the keys if you so wish
  for (var key in previousStories) {
    if (previousStories[key].length > 1) {
      // if we have more than one story on a day, we can just add this to the Stories property
      returnResult.push({
        Date: key,
        Stories: previousStories[key]
      });
    } else if (previousStories[key].length === 1) {
      // if we only have one story, the structure of the return object changes slightly
      returnResult.push({
        Date: key,
        Title: previousStories[key][0].Title
      });
    }
  }

  return returnResult;
}

你的分组涉及相当多的逻辑;在只有一个元素的地方，你想要产生的对象的结构会巧妙地改变，从拥有Stories数组到具有包含那个故事的标题的单一Title属性。也许这个设计可以改进吗？通常更容易对单个数据结构进行编码，而不是基于其多个内容而改变的数据结构。

Answer 3

一旦你想要创建一个Stories对象，当它有titles被分组时，我认为这应该工作：

arr.reduce((acc, ele) => {
    if(acc.length == 0) return acc.concat(ele);
    var previous = acc[acc.length - 1];
    if(ele.Date == previous.Date) {
        if(!previous.Stories) previous.Stories = [{ title: previous.Title }];
            previous.Stories.push({ title: ele.Title })
            delete previous.Title;
        return acc;
    }
return acc.concat(ele);
}, [])