I have data that is coming from the server like this(我有这样的数据来自服务器)
let value = [
{
'commongId': 1,
'principal': true,
'creationDate': '2019-11-03:40:00'
},
{
'commongId': 2,
'principal': false,
'creationDate': '2017-10-25T01:35:00'
},
{
'commongId': 2,
'principal': true,
'creationDate': '2019-05-25T08:00:00'
},
{
'commongId': 1,
'principal': false,
'creationDate': '2018-11-25T09:40:00'
},
{
'commongId': 1,
'principal': false,
'creationDate': '2017-11-25T09:40:00'
},
{
'commongId': 2,
'principal': false,
'creationDate': '2018-05-25T08:00:00'
},
]
I want to transform it in a way that the courses are grouped by commonId , and that the principal course of each 'id' should appear first, and the rest of the courses belonging to the same commonId come after that principal course sorted by the creation date (asc).(我想对它进行某种转换，使课程按commonId分组，并且每个“ id”的主要课程应首先出现，而属于同一commonId的其余课程则在该主要课程之后（按创建顺序排序）日期（升序）。)
So basically the output should be(所以基本上输出应该是)
let value = [
{
commongId: 1,
principal: true,
creationDate: '2019-11-03:40:00'
},
{
commongId: 1,
principal: false,
creationDate: '2017-11-25T09:40:00'
},
{
commongId: 1,
principal: false,
creationDate: '2018-11-25T09:40:00'
},
{
commongId: 2,
principal: true,
creationDate: '2019-05-25T08:00:00'
},
{
commongId: 2,
principal: false,
creationDate: '2017-10-25T01:35:00'
},
{
commongId: 2,
principal: false,
creationDate: '2018-05-25T08:00:00'
}
];
I have a working solution, which in my opinion looks horrible and too complicated.(我有一个可行的解决方案，我认为这看起来太可怕了，太复杂了。)
// function to group the the courses by commonId
const groupBy = (data, keyFn) =>
data.reduce((agg, item) => {
const group = keyFn(item);
agg[group] = [...(agg[group] || []), item];
return agg;
}, {});
let transformedValue = groupBy(courses, item => item.commonId);
//removing the keys from the array of objects
transformedValue = Object.keys(transformedValue).map(k => transformedValue[k]);
// sorting each inner array by creationDate
transformedValue = transformedValue.map(el => {
let modified = el.sort((a, b) =>
moment(a.creationDate).diff(moment(b.creationDate))
);
// pushing the principal object of each array to the top
const foundIndex = modified.findIndex(element => element.principal);
if (foundIndex > -1) {
const foundElement = modified.find(element => element.principal);
modified.splice(foundIndex, 1);
modified.unshift(foundElement);
}
return modified;
});
// flattening the array to one level
transformedValue = transformedValue.flat();
// using the transformed value in the subscription
of(transformedValue).subscribe(p => {
this.dataToShow = p;
});
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