Remove duplicates from a nested array of objects

Question

I'm trying to remove duplicates from a nested array of objects.

let arr = [{
  type: "horizontal",
  tiles: [{ col: 0, row: 3 }, { col: 1, row: 3 }, { col: 2, row: 3 }]
},
{
  type: "horizontal",
  tiles: [{ col: 1, row: 3 }, { col: 2, row: 3 }, { col: 0, row: 3 }]
},
{
  type: "horizontal",
  tiles: [{ col: 2, row: 3 }, { col: 1, row: 3 }, { col: 0, row: 3 }],
},
{
  type: "vertical",
  tiles: [{ col: 0, row: 5 }, { col: 0, row: 3 }, { col: 0, row: 4 }],
}];

I'm trying to only keep the top level objects if they are unique. As you can see the tiles array isn't necessarily sorted by col/row.

So arr here would become:

let arr = [{
  type: "horizontal",
  tiles: [{ col: 0, row: 3 }, { col: 1, row: 3 }, { col: 2, row: 3 }]
},{
  type: "vertical",
  tiles: [{ col: 0, row: 5 }, { col: 0, row: 3 }, { col: 0, row: 4 }],
}];

I've looked extensively but can't quite find something that solves the same problem I'm trying to solve.

Does this answer your question? How to remove all duplicates from an array of objects? — pilchard
– pilchard, Commented Feb 12, 2022 at 16:20
I think you are able to check this url stackoverflow.com/questions/67487238/… — Hu Zhi Xing
– Hu Zhi Xing, Commented Feb 12, 2022 at 16:23
Unfortunately not. I've been looking at that question and have been trying to adapt it but my structure has an extra array surrounding it. — kabatwa
– kabatwa, Commented Feb 12, 2022 at 16:23

cmgchess · Accepted Answer · 2022-02-12 17:27:46Z

0

Okay this may be a little long but I couldn't find a shorter way of doing. My plan was to get a Set of JSON strings (which gives unique) and to convert it back to array of JS objects (Set of JS objects won't remove duplicates). This way will get only the unique values.

But for the JSON strings to be equal for unique records the tiles array has to be in same order so I ran sort on tiles first to make sure the order is same

let arr = [{
  type: "horizontal",
  tiles: [{ col: 0, row: 3 }, { col: 1, row: 3 }, { col: 2, row: 3 }]
},{
  type: "horizontal",
  tiles: [{ col: 1, row: 3 }, { col: 2, row: 3 }, { col: 0, row: 3 }]
},{
  type: "horizontal",
  tiles: [{ col: 2, row: 3 }, { col: 1, row: 3 }, { col: 0, row: 3 }],
},{
  type: "vertical",
  tiles: [{ col: 0, row: 5 }, { col: 0, row: 3 }, { col: 0, row: 4 }],
}];

//sort for ascending order of col field
arr.forEach((o,i,a) => {
    a[i].tiles.sort((a,b) => a.col-b.col)
})


let mySet = new Set();
arr.forEach(item => mySet.add(JSON.stringify(item)))

let result = []
mySet.forEach((el) => {
    result.push(JSON.parse(el))
})


console.log(result)

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

edited Feb 12, 2022 at 17:27

answered Feb 12, 2022 at 17:20

cmgchess

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1 Comment

kabatwa Over a year ago

Thanks for this. I was hoping for something that didn't use JSON.stringify as it seems a little fragile if the sort fails.

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