How to groupby and select max id from object in react native.
that was just a dummy data to explain you that how my object look like
[
{"name": "alex", "subject": "english" "student_id": "1"},
{"name": "hales", "subject": "science" "student_id": "2"},
{"name": "joss", "subject": "english" "student_id": "3"},
{"name": "alexandra", "subject": "science" "student_id": "4"},
{"name": "mark", "subject": "math" "student_id": "5"},
]
First of all I want to group by subject and then select the student with max id so my output should look like that
[
{"name": "joss", "subject": "english" "student_id": "3"},
{"name": "alexandra", "subject": "science" "student_id": "4"},
{"name": "mark", "subject": "math" "student_id": "5"},
]
What I have tried So far is that
const result = myobject.reduce(function (r, a) {
r[a.case_id] = r[a.case_id] || [];
r[a.case_id].push(a);
return r;
}, Object.create(null));
with above code I can group by but not able to get the max id so how could I achieve that?
You could group by subject and replace the value if student_id is greater.
As result take the values from the object.
const
data = [{ name: "alex", subject: "english", student_id: "1" }, { name: "hales", subject: "science", student_id: "2" }, { name: "joss", subject: "english", student_id: "3" }, { name: "alexandra", subject: "science", student_id: "4" }, { name: "mark", subject: "math", student_id: "5" }],
result = Object.values(data.reduce((r, o) => {
if (!r[o.subject] || +r[o.subject].student_id < +o.student_id) {
r[o.subject] = o;
}
return r;
}, Object.create(null)));
console.log(result);.as-console-wrapper { max-height: 100% !important; top: 0; }lodash if don't mind. It seems like a clean and simple way to understand
const data = [{ name: "alex", subject: "english", student_id: "1" }, { name: "hales", subject: "science", student_id: "2" }, { name: "joss", subject: "english", student_id: "3" }, { name: "alexandra", subject: "science", student_id: "4" }, { name: "mark", subject: "math", student_id: "5" }];
const result = _.chain(data)
.groupBy('subject')
.values()
.map((group) => _.maxBy(group, 'student_id'))
.value();
console.log(result);.as-console-wrapper { max-height: 100% !important; top: 0; }<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>