Add key value to an object array if it has same key value

Question

I'm trying to add a property with a certain value to all of the objects in one array, based on a corresponding value in another array.

const array1 = [
  {
    id: 1,
    date: '2022.05.01',
    name: 'john'
  }, {
    id: 2,
    date: '2022.05.01',
    name: 'sam'
  }, {
    id: 3,
    date: '2022.05.03',
    name: 'john'
  }, {
    id: 4,
    date: '2022.05.06',
    name: 'jack'
  },
 ]
    

This array contains the required modifications that need to be made:

const array2 = [
  {
    name: 'john',
    isCanceled: true,
  }, {
    name: 'jack',
    isCanceled: false,
  }, {
    name: 'sam',
    isCanceled: false,
  },
 ]

If the name in the object within array1 is john then isCanceled should be set to true , but if it's jack or sam it should be set to false like so:

const resultArray = [
  {
    id: 1,
    date: '2022.05.01',
    name: 'john',
    isCanceled: true,
  }, {
    id: 2,
    date: '2022.05.01',
    name: 'sam'
    isCanceled: false,
  }, {
    id: 3,
    date: '2022.05.03',
    name: 'john'
    isCanceled: true,
  }, {
    id: 4,
    date: '2022.05.06',
    name: 'jack'
    isCanceled: false,
  },
 ];

Answer 1

Build a status lookup object containing the status, and map your array to include the matching values from the lookup object:

const status = Object.fromEntries(
  array2.map(({name, isCanceled}) => [name, isCanceled])
);

const resultArray = array1.map(({id, date, name}) => ({
  id,
  date,
  name,
  isCanceled: status[name]
}));

Alternatively, if you just want to modify array1 instead of creating a new array, the second step can be replaced with:

array1.forEach(v => v.isCanceled = status[v.name]);

---

Complete snippet:

 const array1 = [{ id: 1, date: '2022.05.01', name: 'john' }, { id: 2, date: '2022.05.01', name: 'sam' }, { id: 3, date: '2022.05.03', name: 'john' }, { id: 4, date: '2022.05.06', name: 'jack' }, ]; const array2 = [{ name: 'john', isCanceled: true, }, { name: 'jack', isCanceled: false, }, { name: 'sam', isCanceled: false, }, ]; const status = Object.fromEntries( array2.map(({name, isCanceled}) => [name, isCanceled]) ); const resultArray = array1.map(({id, date, name}) => ({ id, date, name, isCanceled: status[name] })); console.log(resultArray);

Should you wonder why I prefer to build the lookup object instead of using find() inside the map() operation: in terms of complexity, the lookup table has a complexity of O(1) , while the find() approach is O(n) .

Answer 2

you can do something as :

const result = array1.map(person => {
  const lookPerson = array2.find(person2 => person2.name === person.name);
  return (lookPerson) ? { 
    ...person,
    isCanceled: lookPerson.isCanceled
  } : person;
});

• combine array.map to transform array1

• use array.find to get first iteration of similar person between array1 and array2

• merge object with

  { ...person, isCanceled: lookPerson.isCanceled } 

 const array1 = [{ id: 1, date: '2022.05.01', name: 'john' }, { id: 2, date: '2022.05.01', name: 'sam' }, { id: 3, date: '2022.05.03', name: 'john' }, { id: 4, date: '2022.05.06', name: 'jack' }, ]; const array2 = [{ name: 'john', isCanceled: true, }, { name: 'jack', isCanceled: false, }, { name: 'sam', isCanceled: false, }, ]; const result = array1.map(person => { const lookPerson = array2.find(person2 => person2.name === person.name); return (lookPerson) ? { ...person, isCanceled: lookPerson.isCanceled } : person; }); console.log(result);

Answer 3

You can do this more simply by first converting your array2 into an object and then using a lookup within a map like so:

 const array1 = [{id:1,date:"2022.05.01",name:"john"},{id:2,date:"2022.05.01",name:"sam"},{id:3,date:"2022.05.03",name:"john"},{id:4,date:"2022.05.06",name:"jack"},]; const array2 = [{name:"john",isCanceled:true},{name:"jack",isCanceled:false},{name:"sam",isCanceled:false}]; const arrCancel = array2.reduce((a, { name, isCanceled }) => { a[name] = isCanceled; return a; }, {}); const resultArr = array1.map(e => { e.isCanceled = arrCancel[e.name]; return e; }); console.log(resultArr);

 .as-console-wrapper { max-height: 100% !important; top: auto; }

Answer 4

You can do:

 const array1 = [{id: 1,date: '2022.05.01',name: 'john'}, {id: 2,date: '2022.05.01',name: 'sam'}, {id: 3,date: '2022.05.03',name: 'john'}, {id: 4,date: '2022.05.06',name: 'jack'}] const array2 = [{name: 'john',isCanceled: true,}, {name: 'jack',isCanceled: false,}, {name: 'sam',isCanceled: false,}] const array2Hash = array2.reduce((a, { name: n, isCanceled: ic}) => (a[n] = ic, a), {}) const result = array1.map(u => ({ ...u, isCanceled: array2Hash[u.name] })) console.log(result)

Answer 5

resultArray is map of array1 with addition isCanceled based of array2 :

resultArray = array1.map( a => Object.assign(
  {},
  a,
  {isCanceled: array2.find(b => a.name == b.name)?.isCanceled||false}) )