Javascript - 计算对象数组中的重复项并将计数存储为新对象 [英] Javascript - Counting duplicates in object array and storing the count as a new object

问题描述

我有一组作为产品的 javascript 对象.这些产品以购物车的形式显示在列表中.

我想根据 _.id 值计算数组中重复产品的数量，并从数组中删除这些对象，并将它们与更新版本和名为 count 带有此对象出现的总次数的值.

到目前为止，我已经尝试了很多方法并且我已经在谷歌上进行了搜索，但是我发现没有任何方法可以正确地完成这项工作.

我将使用的数组类型示例如下:

<预><代码>[{_id:5971df93bfef201237985c4d"，弹头:5971df93bfef201237985c4d"，税收百分比:23，总成本:9.99，货币:欧元"，},]

所以我希望我的最终结果是这样的 - 它删除了重复值并将其替换为相同的对象，但添加了一个名为 count 的新键，其值为对象最初的次数在数组中:

<预><代码>[{_id:5971df93bfef201237985c4d"，弹头:5971df93bfef201237985c4d"，税收百分比:23，总成本:9.99，货币:欧元"，count: 2,//无论计数是多少},]

到目前为止，我正在使用这种方法:

变量计数 = [];

if (cart.cart.products != undefined) {让 namestUi = {渲染名称(名称){返回 Array.from(names.reduce((计数器，对象)=>counters.set(object._id, (counters.get(object._id) || 0) + 1),新地图())，([对象，计数]) =>{var filterObj = names.filter(function(e) {返回 e._id == 对象；});返回({filterObj，计数})});}};count = namestUi.renderNames(cart.cart.products);控制台日志(计数)}

但它返回这样的值:

{filterObj: Array//重复的数组，计数:2}{filterObj:数组，计数:1}

并且由于我将 React-Native 与列表视图一起使用，因此这样的事情将不起作用.

它只需要按照之前的方式(一个数组)存储项目，但有一个名为 count 的新子项.

欢迎任何帮助！

解决方案

我会坚持 reduce，使用 Map 并传播它的 values> 得到最终结果:

const names = [{ _id: 1 }, { _id: 1}, { _id: 2}, { _id: 1}];const 结果 = [...names.reduce( (mp, o) => {if (!mp.has(o._id)) mp.set(o._id, { ...o, count: 0 });mp.get(o._id).count++;返回 mp;}, new Map).values()];console.log(result);

或者，您可以先创建地图中所有计数为零的键(使用 Map 构造函数)，然后再次迭代数据以更新计数器.这种任务拆分使代码比 reduce 更简洁:

const names = [{ _id: 1 }, { _id: 1}, { _id: 2}, { _id: 1}];const mp = new Map(names.map(o => [o._id, {...o, count: 0 }]));for (const {_id} of names) mp.get(_id).count++;const 结果 = Array.from(mp.values());console.log(result);

当您拥有多个键时，一种想法是使用 JSON.stringify([ ]) 加入这些键:

const names = [{cat: 1, sub: 1}, {cat: 1, sub: 2}, {cat: 2,子:1}，{猫:1，子:1}]；const 结果 = [...names.reduce( (mp, o) => {const key = JSON.stringify([o.cat, o.sub]);if (!mp.has(key)) mp.set(key, { ...o, count: 0 });mp.get(key).count++;返回 mp;}, new Map).values()];console.log(result);

I have an array of javascript objects that are products. These products are displayed in a list as a cart.

I want to count the number of duplicate products in the array based in the _.id value and remove these objects from the array and relace them with an updated version and a new key called count with a value of the total number of times this object comes up.

So far, I have tried numerous methods and I've searched all over google but there's nothing that I've found that can do the job correctly.

An example of the type of array that I will be using would be this:

[

    {  _id: "5971df93bfef201237985c4d", 
       slug: "5971df93bfef201237985c4d", 
       taxPercentage: 23, 
       totalCost: 9.99, 
       currency: "EUR", 
    },

]

so what I would want my end result to be would be something like this - it removes the duplicate value and replaces it with the same object but adds a new key called count with a value of the number of times the object initially was in the array:

[

    {  _id: "5971df93bfef201237985c4d", 
       slug: "5971df93bfef201237985c4d", 
       taxPercentage: 23, 
       totalCost: 9.99, 
       currency: "EUR", 
       count: 2, // whatever the count is
    },

]

So far I'm using this method:

var count = [];

if (cart.cart.products != undefined) {
    let namestUi = {
        renderNames(names){
            return Array.from(
                names.reduce( (counters, object) =>
                        counters.set(object._id, (counters.get(object._id) || 0) + 1),
                    new Map() ),
                ([object, count]) => {
                    var filterObj = names.filter(function(e) {
                        return e._id == object;
                    });

                    return ({filterObj, count})
                }
            );
        }
    };

    count = namestUi.renderNames(cart.cart.products);
    console.log(count)
}

but it returns the values like this:

{filterObj: Array // the array of the duplicates, count: 2}
{filterObj: Array, count: 1}

and since I am using React-Native with a list view something like this won't work.

It just needs to store the items the way it was before (an array) but with a new child called count.

Any help is welcomed!

解决方案

I would stick to reduce, use a Map and spread its values to get the final result:

const names = [{  _id: 1 }, { _id: 1}, { _id: 2}, { _id: 1}];

const result = [...names.reduce( (mp, o) => {
    if (!mp.has(o._id)) mp.set(o._id, { ...o, count: 0 });
    mp.get(o._id).count++;
    return mp;
}, new Map).values()];

console.log(result);

Or you can first create all the keys in the map with a zero count (using the Map constructor), and then iterate the data again to update the counter. This split of tasks makes the code more concise than with reduce:

const names = [{  _id: 1 }, { _id: 1}, { _id: 2}, { _id: 1}];

const mp = new Map(names.map(o => [o._id, {...o, count: 0 }]));
for (const {_id} of names) mp.get(_id).count++;
const result = Array.from(mp.values());

console.log(result);

When you would have more than one key, then one idea is to join those with JSON.stringify([ ]):

const names = [{cat: 1, sub: 1}, {cat: 1, sub: 2}, {cat: 2, sub: 1}, {cat: 1, sub: 1}];

const result = [...names.reduce( (mp, o) => {
    const key = JSON.stringify([o.cat, o.sub]);
    if (!mp.has(key)) mp.set(key, { ...o, count: 0 });
    mp.get(key).count++;
    return mp;
}, new Map).values()];

console.log(result);

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