在javascript中比较和合并数组

Question

const arr1 = [{id:1, checked:false},{id:2, checked:false},{id:3, checked:false}]

const arr2 = [{id:1},{id:3}]

i have 2 arrays like above. i want to result should be

arr1 = [{id:1, checked:true},{id:2, checked:false},{id:3, checked:true}]

i tried with array filter, but it gives joined array

companyArr.forEach(citem => {
        mapItem.forEach(mitem => {
            companyArr.push({
            Id: citem.Id,
            CompanyName: citem.CompanyName,
            isChecked: (mitem.company_id === citem.Id)
          })
        })
      })

Answer 1

You could make a Set which keeps all your ids from each object in arr2 , and then use .map() on arr1 to check the checked values based on whether the set has the current objects id:

 const arr1 = [{id:1, checked:false},{id:2, checked:false},{id:3, checked:false}] const arr2 = [{id:1},{id:3}]; const lut = new Set(arr2.map(({id}) => id)); const res = arr1.map(o => ({...o, checked: lut.has(o.id)})) console.log(res);

 .as-console-wrapper { max-height: 100% !important; top: 0; } /* ignore */

Note: I've created a set here for efficient lookup, however, you could use .some() on arr2 if you wish in the .map() as well, but this would have performance drawbacks for large data sets:

 const arr1 = [{id:1, checked:false},{id:2, checked:false},{id:3, checked:false}] const arr2 = [{id:1},{id:3}]; const res = arr1.map(o => ({...o, checked: arr2.some(({id}) => id === o.id)})); console.log(res);

 .as-console-wrapper { max-height: 100% !important; top: 0; } /* ignore */

Answer 2

you could use Array#map for recreate the array .And Array#findIndex for find the first array value exist on 2nd array .And use Spread operator for easy to split the object

 const arr1 = [{id:1, checked:false},{id:2, checked:false},{id:3, checked:false}] const arr2 = [{id:1},{id:3}] let res = arr1.map(a=> ({...a,checked: arr2.findIndex(({id}) => id == a.id) > -1})); console.log(res)

Answer 3

You can use map and find for that.

 const arr1 = [{ id: 1, checked: false }, { id: 2, checked: false }, { id: 3, checked: false }] , arr2 = [{ id: 1 }, { id: 3 }] , result = arr1.map(el => ({ ...el, checked: !!arr2.find(({ id }) => id === el.id) })); console.log(result);