Filter array of objects with another array of objects and add extra key to matching objects

Question

I have following two arrays, I want to get second array, but matching objects should contain one more extra key "select" : true, and not matching objects should contain "select" : false.

var firstArray = [{id: -1, type: "group"},
                  {id: -2, type: "group"}];

var secondArray = [{id: -3, type: "group"},
                   {id: -2, type: "group"},
                   {id: -1, type: "group"}];

Expected outcome:

var expectedArray = [{id: -1, type: "group", select: true},
                     {id: -2, type: "group", select: true},
                     {id: -3, type: "group", select: false}];

I have tried below code:

for(var i=0;i<firstArray.length;i++){
             for(var j=0;j<secondArray.length;j++){
               console.log(firstArray[i].id,secondArray[j].id)
               if(firstArray[i].id===secondArray[j].id){
                 if(secondArray[j].hasOwnProperty('select')){
                   secondArray[j].select=true;
                   // console.log('true select property',secondArray[j].select)
                 }
                 else{
                   secondArray[j].select=true;
                   // console.log('true adding new',secondArray[j].select)
                 }
               }else{
                  secondArray[j]['select']=false;
                 // console.log('false not match',secondArray[j].select)
               }
             }
          }

@user11299053, Sure, It works, Please upvote to my question. — Kunvar Singh
– Kunvar Singh, Commented Apr 30, 2019 at 3:09

adiga · Accepted Answer · 2019-04-26 11:10:08Z

4

You could create a Set of all the ids which are present in firstArray. Then loop through the secondArray using forEach and add select value based on whether the set has the id

let firstArray=[{id:-1,type:"group"},{id:-2,type:"group"}],
    secondArray=[{id:-3,type:"group"},{id:-2,type:"group"},{id:-1,type:"group"}];

const ids = new Set(firstArray.map(a => a.id));
secondArray.forEach(a => a.select = ids.has(a.id))

console.log(secondArray)

answered Apr 26, 2019 at 11:10

adiga

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Comments

Yevhen Horbunkov · Accepted Answer · 2019-04-26 14:59:32Z

1

You can do that with just one line of code:

var firstArray = [
	{id: -1, type: "group"}, 
	{id: -2, type: "group"}
];

var secondArray = [
	{id: -3, type: "group"}, 
	{id: -2, type: "group"}, 
	{id: -1, type: "group"}
];

const result = secondArray.map(item => ({...item, 'select': firstArray.some(entry => entry.id == item.id)}));

console.log(result);

.as-console-wrapper {
  max-height: 100% !important;
  color: white;
  top: 0;
}

.as-console-row {
  background: black;
}

edited Apr 26, 2019 at 14:59

answered Apr 26, 2019 at 11:35

Yevhen Horbunkov

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Comments

lone_worrior · Accepted Answer · 2019-04-26 11:10:27Z

1

This should work :

var ans = secondArray.map(s=> {
var match = firstArray.find(f=> f.id === s.id);
if(match) s['select'] = true;
else s['select'] = false;
return s;
})

answered Apr 26, 2019 at 11:10

lone_worrior

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Comments

deerawan · Accepted Answer · 2019-04-26 11:52:09Z

1

Instead of modifying the secondArray, it is better to not modify it directly. We can use immutable way by creating another array that has select property. For this case, we will use map.

var firstArray = [{id: -1, type: "group"},
                  {id: -2, type: "group"}];

var secondArray = [{id: -3, type: "group"},
                   {id: -2, type: "group"},
                   {id: -1, type: "group"}];

const expectedArray = secondArray.map(item => {
  const idExist = firstArray.find(itemInFirst => itemInFirst.id === item.id);
  return {
    ...item,
    select: idExist !== undefined
  }
});

console.log(expectedArray);

answered Apr 26, 2019 at 11:52

deerawan

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