How to map array one to many relationship in Javascript

Question

I am trying to convert following JSON data using map function into appropriate output

[{"jobId":100049,"name":"Drilling","jobNumber":"1222455","address":"Ahmedabad","city":"Ahmedabad","state":"1","zip":"38003","active":true,"jobOwnerId":100002,"jobOwnerName":"Troy Thomson","createdBy":"","createdOn":"2020-03-15T18:42:25.6533333","modifiedBy":"","modifiedOn":"2020-03-16T13:21:53.0333333","members":[{"memberId":100001,"memberName":"Hardik Gondalia"},{"memberId":100004,"memberName":"Micheal T. Angelo"}],"assets":[{"assetId":100004,"assetName":"Minima ullam non mol"}]},{"jobId":100051,"name":"Drilling The Hole","jobNumber":"11111","address":"201, AA 333 Steet, Time Square","city":"Boston","state":"1","zip":"11111","active":true,"jobOwnerId":100001,"jobOwnerName":"Hardik Gondalia","createdBy":"","createdOn":"2020-03-25T11:12:13.89","modifiedBy":"","modifiedOn":"2020-03-25T11:12:32.1266667","members":[{"memberId":100002,"memberName":"Troy Thomson"}],"assets":[{"assetId":100005,"assetName":"Drill Machine P2222"}]}]

Desired Output:

[{"jobid":100049,"memberid":100001],{"jobid":100049,"memberid":100004],{"jobid":100051,"memberid":100002]}

As you can see job is json object and have array of members and assets inside it. I want to repeat jobid if it has multiple member or assets.

What I've tried is:

const assignmentAssetModel = this.jobList.map(i => ({ jobid: i.jobId, assetid: i.assets.map(j => j.assetId) }));

But it gives me following output:

[{"jobid":100049,"memberid":[100001,100004]},{"jobid":100051,"memberid":[100002]}]

As you can I want to repeat jobid if it has more then one memberid

Answer 1

You can use Array.reduce() instead of Array.map() since the length of the result array is different then the initial array.

 const jobList = [{"jobId":100049,"name":"Drilling","jobNumber":"1222455","address":"Ahmedabad","city":"Ahmedabad","state":"1","zip":"38003","active":true,"jobOwnerId":100002,"jobOwnerName":"Troy Thomson","createdBy":"","createdOn":"2020-03-15T18:42:25.6533333","modifiedBy":"","modifiedOn":"2020-03-16T13:21:53.0333333","members":[{"memberId":100001,"memberName":"Hardik Gondalia"},{"memberId":100004,"memberName":"Micheal T. Angelo"}],"assets":[{"assetId":100004,"assetName":"Minima ullam non mol"}]},{"jobId":100051,"name":"Drilling The Hole","jobNumber":"11111","address":"201, AA 333 Steet, Time Square","city":"Boston","state":"1","zip":"11111","active":true,"jobOwnerId":100001,"jobOwnerName":"Hardik Gondalia","createdBy":"","createdOn":"2020-03-25T11:12:13.89","modifiedBy":"","modifiedOn":"2020-03-25T11:12:32.1266667","members":[{"memberId":100002,"memberName":"Troy Thomson"}],"assets":[{"assetId":100005,"assetName":"Drill Machine P2222"}]}] const jobsPerMember = jobList.reduce((acc, cur) => { cur.members.forEach((member) => acc.push({ jobid: cur.jobId, memberid: member.memberId })) return acc },[]) console.log(jobsPerMember)

Answer 2

You could take Array#flatMap and map the outer and inner properties.

 var data = [{ jobId: 100049, name: "Drilling", jobNumber: "1222455", address: "Ahmedabad", city: "Ahmedabad", state: "1", zip: "38003", active: true, jobOwnerId: 100002, jobOwnerName: "Troy Thomson", createdBy: "", createdOn: "2020-03-15T18:42:25.6533333", modifiedBy: "", modifiedOn: "2020-03-16T13:21:53.0333333", members: [{ memberId: 100001, memberName: "Hardik Gondalia" }, { memberId: 100004, memberName: "Micheal T. Angelo" }], assets: [{ assetId: 100004, assetName: "Minima ullam non mol" }] }, { jobId: 100051, name: "Drilling The Hole", jobNumber: "11111", address: "201, AA 333 Steet, Time Square", city: "Boston", state: "1", zip: "11111", active: true, jobOwnerId: 100001, jobOwnerName: "Hardik Gondalia", createdBy: "", createdOn: "2020-03-25T11:12:13.89", modifiedBy: "", modifiedOn: "2020-03-25T11:12:32.1266667", members: [{ memberId: 100002, memberName: "Troy Thomson" }], assets: [{ assetId: 100005, assetName: "Drill Machine P2222" }] }], result = data.flatMap(({ jobId, members }) => members.map(({ memberId }) => ({ jobId, memberId }))); console.log(result);

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Answer 3

You should use the .reduce method instead:

this.jobList.reduce((acc, { members, jobId }) => {
   return [...acc, ...members.map(({ memberId }) => ({ jobId, memberId }))]; 
}, []);

If you're targeting more recent version of javascript (ES2019), you can also use flatMap:

this.jobList.flatMap(({ members, jobId }) => members.map(({ memberId }) => ({ jobId, memberId })));