I have two arrays, I'm trying to update the object of the first array with the object from the second array if name is changed. I can do that with nested loop but I can't figured out with .map() and .some() methods

const result1 = [{
    "id": 1,
    "name": "name1"
},
{
    "id": 2,
    "name": "name2"
}]

const result2 = [{
    "id": 1,
    "name": "name1"
},
{
    "id": 2,
    "name": "changed"
}]

Here is the nested loop version that works:

for (i = 0; i < result1.length; i  ) {
    for (ii = 0; ii < result2.length; ii  ) {

        if (result1[i].id == result2[ii].id && result1[i].name !== result2[ii].name) {
            result1[i].name = result2[ii].name
        }

    }
}

console.log(result1)

I get the correct result:

result1 = [ { id: 1, name: 'result1_name1' }, { id: 2, name: 'changed' } ]

And now I tried:

result1.map(res1 => {

    let response = !result2.some(res2 => res1.name === res2.name)

    if (response) {
        res1.name = res2.name
    }
    return response
})

console.log(result1)

But I get an error:

ReferenceError: res2 is not defined

How can I do that?

Edit: Sorry, I changed to first paragraph because my issue was a bit different

CodePudding user response：

res2 is only accessible in the scope of the callback provided to .some(). Therefore it's undefined outside that scope.

And secondly, I think there's a logic error in your comparison. It seems like you need to compare the values as well as the IDs of the records.

const result1 = [ { id: 1, name: "name1" }, { id: 2, name: "name2" } ],
      result2 = [ { id: 1, name: "name1" }, { id: 2, name: "changed" } ];

const changedResult1 = result1.map(item => ({
  ...item,
  name: result2.find(item2 => item2.id === item.id)?.name || item.name
}))

console.log(changedResult1)

CodePudding user response：

One approach is to create a dictionary of result2(where id will be key & name as value) & then put map on result1 to get the desired result.

const result1 = [{"id": 1, "name": "name1"},{"id": 2,"name": "name2"}];

const result2 = [{"id": 1, "name": "name1"},{"id": 2,"name": "changed"}];

const dict = Object.fromEntries(result2.map(o=>[o.id, o.name]));
const updated = result1.map(o=>({...o, name:dict[o.id] }));
console.log(updated);

CodePudding user response：

Because you did not declare res2 in your res1 map.

You can find it with filter as ;

result1.map(res1 => {

    let response = result2.filter(res2 => res1.name !== res2.name)

    if (response.length > 0) {
        res1.name = response[0].name
    }
    return response
})

console.log(result1)

CodePudding user response：

You can simply iterate result2 with forEach, replacing the corresponding (by id) object's name in result1 with the one from result2:

const result1 = [{
    "id": 1,
    "name": "name1"
},
{
    "id": 2,
    "name": "name2"
}]

const result2 = [{
    "id": 1,
    "name": "name1"
},
{
    "id": 2,
    "name": "changed"
}]

result2.forEach(({ id, name }) => result1[result1.findIndex(o => o.id == id)].name = name)

console.log(result1)

Note that it's safe to always copy the name from result2 as if it is the same, it will not affect the value in result1.

CodePudding user response：

You could use Array.reduce() to group the items by id using a Map.

const result1 = [{ "id": 1, "name": "name1" }, { "id": 2, "name": "name2" }]
const result2 = [{ "id": 1, "name": "name1" }, { "id": 2, "name": "changed" }] 

const result = [...([...result1, ...result2].reduce((map, item) => { 
    return map.set(item.id, item);
}, new Map())).values()]

console.log('Result:', result)

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