合并对象数组中的重复对象

I have below array of objects,

我有下面的对象数组，

var data = [
    {
        label: "Book1",
        data: "US edition"
    },
    {
        label: "Book1",
        data: "UK edition"
    },
    {
        label: "Book2",
        data: "CAN edition"
    }
];

I want to merge the duplicate objects based on attribute 'label' so that Final output will look like below,

我想基于属性'label'合并重复的对象，以便最终输出如下所示，

var data = [
    {
        label: "Book1",
        data: ["US edition", "UK edition"] //data attribute is merged
    },
    {
        label: "Book2",
        data: "CAN edition"
    }
];

Can someone help me identify the approach?

有人可以帮我确定方法吗？

2 个解决方案

#1

I would probably loop through with filter, keeping track of a map of objects I'd seen before, along these lines (edited to reflect your agreeing that yes, it makes sense to make (entry).data always an array):

我可能会使用过滤器循环，跟踪我之前看到的对象的地图，沿着这些线（编辑以反映您同意是的，使（入口）.data总是一个数组是有意义的）：

var seen = {};
data = data.filter(function(entry) {
    var previous;

    // Have we seen this label before?
    if (seen.hasOwnProperty(entry.label)) {
        // Yes, grab it and add this data to it
        previous = seen[entry.label];
        previous.data.push(entry.data);

        // Don't keep this entry, we've merged it into the previous one
        return false;
    }

    // entry.data probably isn't an array; make it one for consistency
    if (!Array.isArray(entry.data)) {
        entry.data = [entry.data];
    }

    // Remember that we've seen it
    seen[entry.label] = entry;

    // Keep this one, we'll merge any others that match into it
    return true;
});

In an ES6 environment, I'd use seen = new Map() rather than seen = {}.

在ES6环境中，我使用seen = new Map（）而不是看到= {}。

Note: Array.isArray was defined by ES5, so some quite older browsers like IE8 won't have it. It can easily be shimmed/polyfilled, though:

注意：Array.isArray是由ES5定义的，因此像IE8这样的一些相当老的浏览器将不具备它。它可以很容易地进行垫片/聚合填充，但是：

if (!Array.isArray) {
    Array.isArray = (function() {
        var toString = Object.prototype.toString;
        return function(a) {
            return toString.call(a) === "[object Array]";
        };
    })();
}

Side note: I'd probably also always make entry.data an array, even if I didn't see two values for it, because consistent data structures are easier to deal with. I didn't do that above because your end result showed data being just a string when there was only one matching entry. (We've done that above now.)

旁注：我可能也总是使entry.data成为一个数组，即使我没有看到它的两个值，因为一致的数据结构更容易处理。我之前没有这样做，因为当只有一个匹配条目时，最终结果显示数据只是一个字符串。（我们现在已经完成了。）

Live example (ES5 version):

实例（ES5版）：

var data = [
    {
        label: "Book1",
        data: "US edition"
    },
    {
        label: "Book1",
        data: "UK edition"
    },
    {
        label: "Book2",
        data: "CAN edition"
    }
];
snippet.log("Before:");
snippet.log(JSON.stringify(data, null, 2), "pre");
var seen = {};
data = data.filter(function(entry) {
    var previous;

    // Have we seen this label before?
    if (seen.hasOwnProperty(entry.label)) {
        // Yes, grab it and add this data to it
        previous = seen[entry.label];
        previous.data.push(entry.data);

        // Don't keep this entry, we've merged it into the previous one
        return false;
    }

    // entry.data probably isn't an array; make it one for consistency
    if (!Array.isArray(entry.data)) {
        entry.data = [entry.data];
    }

    // Remember that we've seen it
    seen[entry.label] = entry;

    // Keep this one, we'll merge any others that match into it
    return true;
});
snippet.log("After:");
snippet.log(JSON.stringify(data, null, 2), "pre");

<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

#2

This code is tested on latest version of firefox. To work on other browsers change Array.isArray for a library as lodash or whatever you prefer.

此代码在最新版本的Firefox上测试。要在其他浏览器上工作，请将库的Array.isArray更改为lodash或您喜欢的任何内容。

var data = [
    {
        label: "Book1",
        data: "US edition"
    },
    {
        label: "Book1",
        data: "UK edition"
    },
    {
        label: "Book2",
        data: "CAN edition"
    }
],
i = 0,
j = data.length - 1,
current;

for (;i < data.length; i++) {
  current = data[i];
  for (;j > i; j--) {
     if (current.label === data[j].label) {
       if (Array.isArray(current.data)) {
         current.data = current.data.concat([data[j].data]);
       } else {
         current.data = [].concat([data[j].data, current.data]);
       }
       data.splice(j, 1);
     }

  }
} 

console.log(data);

#1