[英]Merge objects in array by value and get count for each
Given the following array of objects:给定以下对象数组:
myArray = [
{
item: 'Item 1',
material: 'Material1',
type: 'head'
},
{
item: 'Item 1',
material: 'Material1',
type: 'head'
},
{
item: 'Item 2',
material: 'Material2',
type: 'shell'
},
{
item: 'Item 1',
material: 'Material1',
type: 'head'
},
{
item: 'Item 2',
material: 'Material2',
type: 'shell'
},
{
item: 'Item 3',
material: 'Material3',
type: 'support'
},
{
item: 'Item 1',
material: 'Material1',
type: 'head'
},
{
item: 'Item 3',
material: 'Material3',
type: 'support'
},
{
item: 'Item 2',
material: 'Material2',
type: 'shell'
}
]
I need to combine these by the item
value with a count so that I get an array that looks like this:我需要将这些按
item
值与计数结合起来,以便得到一个如下所示的数组:
var myResultArray = [
{
item: 'Item 1',
material: 'Material1',
type: 'head'
count: 4
},
{
item: 'Item 2',
material: 'Material2',
type: 'shell'
count: 3
},
{
item: 'Item 3',
material: 'Material3',
type: 'support'
count: 2
},
]
What is the easiest way to do this?最简单的方法是什么? I'm partial to Lodash, but I'm open to other alternatives.
我偏爱 Lodash,但我对其他选择持开放态度。 With
_.groupBy()
I can get everything grouped together with the item as the object key:使用
_.groupBy()
我可以将所有内容与项目组合在一起作为对象键:
var myGrouped = _.groupBy(myArray, 'item');
but that only gets me part way there.但这只会让我走到那一步。 Searching around here I see a lot of uses of
_.reduce()
(or just plain .reduce()
) or _.map()
, but I haven't been able to get my head around exactly how to use them in this case.在这里搜索我看到很多
_.reduce()
(或只是普通的 .reduce .reduce()
)或_.map()
的用途,但我一直无法确切地了解如何在此使用它们案件。 If I try to use _.groupBy()
chained with _.map()
like so如果我尝试像这样使用
_.groupBy()
与_.map()
) 链接
var myGrouped = _(myArray).groupBy('item').map(function(item) {
// do stuff here
});
the execution doesn't even get to my map function, so I'm not sure what I'm doing wrong.执行甚至没有到达我的地图功能,所以我不确定我做错了什么。
Thanks.谢谢。
_.groupBy
chained with _.map
is the simplest solution. _.groupBy
与_.map
链接是最简单的解决方案。 A proper callback function for the _.map
would be: _.map
的适当回调函数是:
function (items) {
items[0].count = items.length;
return items[0];
}
Or you could condense it further with ES6 arrow-functions.或者你可以用 ES6 箭头函数进一步压缩它。
const myArray = [{"item":"Item 1","material":"Material1","type":"head"},{"item":"Item 1","material":"Material1","type":"head"},{"item":"Item 2","material":"Material2","type":"shell"},{"item":"Item 1","material":"Material1","type":"head"},{"item":"Item 2","material":"Material2","type":"shell"},{"item":"Item 3","material":"Material3","type":"support"},{"item":"Item 1","material":"Material1","type":"head"},{"item":"Item 3","material":"Material3","type":"support"},{"item":"Item 2","material":"Material2","type":"shell"}]; const myResultArray = _(myArray).groupBy('item').map(items => (items[0].count = items.length, items[0])).value(); console.log(myResultArray);
<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>
If you want to do it without using Lodash, this would create the required array:如果您想在不使用 Lodash 的情况下执行此操作,这将创建所需的数组:
const res = myArray.reduce((accum, val) => {
let summary = accum.get(val.item) || Object.assign({}, val, {count:0});
summary.count++;
return accum.set(val.item, summary);
}, new Map());
console.log([...res.values()]);
I ended up going with this:我最终选择了这个:
var groupedData = [];
_(typeData).groupBy('item').forEach(function(value, key) {
var obj = {};
obj.count = value.length;
obj.type = value[0].type;
obj.details = value[0].details;
obj.description = key;
groupedData.push(obj);
});
using _.countBy
and _.uniqBy
使用
_.countBy
和_.uniqBy
var res = _.chain(myArray)
.countBy('item') // get each item count
.thru(counts => // counts = {Item 1: 4, Item 2: 3, Item 3: 2}
_.chain(myArray)
.uniqBy('item') // get uniq items
.map(item => // set each item count
_.assign(
item,
{count: counts[item.item]}
);
)
.value();
)
.value();
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