如何在Javascript中按键合并数组和分组？

Question

I have multiple array in reactjs.

{last_name: 'User1', status: 'BRONZE', type: 'Maintenance', due_date: '2022-06-04 00:00:00'}
{last_name: 'User1', status: 'BRONZE', type: 'Contrôle technique', due_date: '2022-06-18 00:00:00'}
{last_name: 'User2', status: 'BRONZE', type: 'Unknow', due_date: null}

I would like to merge the array by user last_name to have a result like this:

{last_name: 'User1', status1: 'BRONZE', type: 'Maintenance1', due_date1: '2022-06-04 00:00:00', status2: 'BRONZE', type2: 'Contrôle technique', due_date: '2022-06-18 00:00:00'}
{last_name: 'User2', status: 'BRONZE', type: 'Unknow', due_date: null}

In my example I have merge the array 1 and 2 to have 1 array "group by" last_name, here User1 but I need to keep the value of the second array too.

Answer 1

Your question lacks a few details. Are status and due_date the only fields that might be repeated? If so, the below answer should work. If not, you might want to specify which keys should be merged with an index in the field name, and which can be pulled in as is.

I'm not sure why you would want to structure your data this way-- having different field names seems like it would make it difficult to find the data, but leaving that aside:

 const data = [{ last_name: 'User1', status: 'BRONZE', type: 'Maintenance', due_date: '2022-06-04 00:00:00' }, { last_name: 'User1', status: 'BRONZE', type: 'Contrôle technique', due_date: '2022-06-18 00:00:00' }, { last_name: 'User2', status: 'BRONZE', type: 'Unknow', due_date: null }] const mergedMap = {} // Group list elements by last_name for (const el of data) { if (el.last_name in mergedMap) { mergedMap[el.last_name].push(el) } else { mergedMap[el.last_name] = [el] } } // Iterate over "user" groups, modifying field names. const mergedList = [] for (const last_name in mergedMap) { const elCount = mergedMap[last_name].length // If there's only one entry for this "last_name", keep it as is, // then continue to next user. if (elCount === 1){ mergedList.push(mergedMap[last_name][0]) continue } const mergedUser = mergedMap[last_name].reduce((merged, el, index) => ({ // Keep whatever keys are already here ...merged, // last_name and status are assumed to always be the same // for a given user, so they're safe to overwrite each time last_name: el.last_name, status: el.status, // type and due_date might be unique for each entry, so // we add an index to the field name and copy the new value in [`type${index + 1}`]: el.type, [`due_date${index + 1}`]: el.due_date, }), {}) mergedList.push(mergedUser) } console.log(JSON.stringify(mergedList, null, 2))