Javascript 使用 Lodash 按键对值求和
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Using Lodash to sum values by key
提问by S. Hussey
How can I sum the values in objects which share a common key? I needto use Lodash for this because I need good performance if these arrays get huge.
如何对共享公共键的对象中的值求和？我需要为此使用 Lodash，因为如果这些数组变得很大，我需要良好的性能。
var prjMgrValues = [
{"proj_mgr":"Hyman ProjManager","submitted_dollars":12000},
{"proj_mgr":"Hyman ProjManager","submitted_dollars":750000},
{"proj_mgr":"Joe ProjManager","submitted_dollars":45000}
]
I'm looking for an output of
我正在寻找输出
[
{"proj_mgr":"Hyman ProjManager","submitted_dollars":762000},
{"proj_mgr":"Joe ProjManager","submitted_dollars":45000}
]
回答by 4castle
This is a case of reduction for each unique element.
这是对每个唯一元素进行归约的情况。
I always use _.groupByand then _.mapthe result to an array after applying the reduction. In this case the reduction operation is _.sumBy.
我总是使用_.groupBy然后_.map在应用减少后将结果转换为数组。在这种情况下，归约操作是_.sumBy。
var prjMgrValues = [
{"proj_mgr":"Hyman ProjManager","submitted_dollars":12000},
{"proj_mgr":"Hyman ProjManager","submitted_dollars":750000},
{"proj_mgr":"Joe ProjManager","submitted_dollars":45000}
];
var output =
_(prjMgrValues)
.groupBy('proj_mgr')
.map((objs, key) => ({
'proj_mgr': key,
'submitted_dollars': _.sumBy(objs, 'submitted_dollars') }))
.value();
console.log(output);<script src="https://cdn.jsdelivr.net/lodash/4.14.1/lodash.min.js"></script>