如何合并来自两个 arrays 的对象

Question

I have two arrays of objects

    let current = [
        {
            categoryId: 18,
            id: 'fire_18',
            test: 'test'
        }, {
            oldItem: "items that dont exist in new array should be deleted"
        }
    ]

    let new_data = [
        {
            id: 'fire_18',
            categoryId: 18,
            test1: 'test1',
        }, {
            newItem: "new items should be added to final"
        }
    ]

I need to merge those so the result is not missing data from current array. The desired result looks like this

    [
        {
            id: 'fire_18',
            categoryId: 18,
            test1: 'test1',
            test: 'test'
        }, {
            newItem: "new items should be added to final"
        }
    ]

Here is my attempt

 let current = [ { categoryId: 18, id: 'fire_18', test: 'test' }, { oldItem: "items that dont exist in new array should be deleted" } ] let new_data = [ { id: 'fire_18', categoryId: 18, test1: 'test1', }, { newItem: "new items should be added to final" } ] console.log(' === Current ==>', current); console.log(' === New ==>', new_data); new_data.map(newItem => { let currentMatch; try { // incase new item newItem.categoryId wont exist currentMatch = current.find(c => c.categoryId == newItem.categoryId) || {}; } catch (error) { // in that case, no need to merge currentMatch = {}; } return Object.assign(currentMatch, newItem); }); console.log(' === Merged ==>', new_data);

the main thing wrong still is test key from the current arr is missing after merge.

Can anyone modify the pen to not delete keys from the current arr?

Answer 1

Note that Array.map method returns a new array. You are not logging this merged new array - but one of your old arrays.

Also, you don't need try catch here. You may also note that if the categoryId is undefined, the objects will still match. So, you need a check for that.

 let current = [ { categoryId: 18, id: 'fire_18', test: 'test' }, { oldItem: "items that dont exist in new array should be deleted" } ] let new_data = [ { id: 'fire_18', categoryId: 18, test1: 'test1', }, { newItem: "new items should be added to final" } ] newArray = new_data.map(newItem => { let currentMatch; currentMatch = current.find(c => c.categoryId === newItem.categoryId && newItem.categoryId) || {}; return Object.assign(currentMatch, newItem); }); console.log(' === Merged ==>', newArray);

Answer 2

You can use lodash for this.

finalArr = _(_.flatten([current, new_data]))
                                        .groupBy('id')
                                        .map(_.spread(_.assign))
                                        .value();

Answer 3

Like this? I'm not sure what you're expecting to happen with the newItem and oldItem entries.

 let current = [{ categoryId: 18, id: 'fire_18', test: 'test' }] let new_data = [{ id: 'fire_18', categoryId: 18, test1: 'test1', }] const result = Object.values([...current, ...new_data].reduce((acc, { categoryId, ...other }) => ({...acc, [categoryId]: { categoryId, ...other } }), {})); console.log(result);

Answer 4

You can use es6 spread operator to meet your requirement

  var current = [{
    categoryId: 18,
    id: 'fire_18',
    name: 'Servers',
    slugName: 'fire_18',
    test: 'test'
}]

var new_data = [{
    id: 'fire_18',
    categoryId: 18,
    name: 'Servers',
    slugName: 'fire_18'
}]

const results = new_data.map(item => {
    let newItem = { ...item };
    const currentMatchItem = current.find(c => c.categoryId == newItem.categoryId);

    if (currentMatchItem) {
        newItem = { ...currentMatchItem, ...newItem };
    }

    return newItem;
});

console.log(results);

Answer 5

I found this . On your code it goes like that:

 let current = [ { categoryId: 18, id: 'fire_18', test: 'test' }, { oldItem: "items that dont exist in new array should be deleted" } ] let new_data = [ { id: 'fire_18', categoryId: 18, test1: 'test1', }, { newItem: "new items should be added to final" } ] function merge(a, b, prop){ var reduced = a.filter(function(aitem){ return. b;find(function(bitem){ return aitem[prop] === bitem[prop]; }); }). return reduced;concat(b). } console,log(merge(current, new_data; "id") );