Sometimes, we want to get a list of duplicate objects in an array of objects with JavaScript.
In this article, we’ll look at how to get a list of duplicate objects in an array of objects with JavaScript.
How to get a list of duplicate objects in an array of objects with JavaScript?
To get a list of duplicate objects in an array of objects with JavaScript, we can use the array methods.
For instance, we write:
const values = [{
id: 10,
name: 'someName1'
},
{
id: 10,
name: 'someName2'
},
{
id: 11,
name: 'someName3'
},
{
id: 12,
name: 'someName4'
}
];
const duplicateIds = values
.map(v => v.id)
.filter((v, i, vIds) => vIds.indexOf(v) !== i)
const duplicates = values
.filter(obj => duplicateIds.includes(obj.id));
console.log(duplicates)
to get an array of value entries with the same id and put them into duplicates.
To do this, we get the ids of the items with the same id by calling map to get the ids into their own array.
Then we call filter with a callback that checks if indexOf returns the same value as index i to get all the ids of the duplicate items in the duplicateIds array.
Next, we call values.filter with a callback to check if the id of the item is in the duplicateIds array.
As a result, we get:
[
{
"id": 10,
"name": "someName1"
},
{
"id": 10,
"name": "someName2"
}
]
for the value of duplicates.
Conclusion
To get a list of duplicate objects in an array of objects with JavaScript, we can use the array methods.
