react I want to remove duplicate values in the array

Question

If there is the same id in the array, I want to delete it.
In the following, id3 and id4 are duplicated. I want to delete the duplicates and create an array like ①.
I used indexof as shown below, but I can't get rid of duplicate values from the array.
If anyone knows, I would like to ask a professor

// users
     {id:1, name: 'aaaaa', type: "text"}
     {id:2, name: 'bbbbb', type: "text"}
     {id:3, name: 'ccccc', type: "text"}
     {id:3, name: 'dddddd', type: "text"}
     {id:4, name: 'eeeeee', type: "text"}
     {id:4, name: 'ffffff', type: "text"}

//①Array with duplicates removed
 {id:1, name: 'aaaaa', type: "text"}
 {id:2, name: 'bbbbb', type: "text"}
 {id:3, name: 'dddddd', type: "text"}
 {id:4, name: 'ffffff', type: "text"}

  const List = (users:Users[]) => {
    const arrayUsers = users.filter((x, i, self) => {
      return self.indexOf(x) === i;
    });

mr hr · Answer 1 · 2020-12-08T07:41:10.713

2

You could use Array.prototype.reduce() method to remove the duplicates. Traverse the array and group it by id.

const users = [
  { id: 1, name: 'aaaaa', type: 'text' },
  { id: 2, name: 'bbbbb', type: 'text' },
  { id: 3, name: 'ccccc', type: 'text' },
  { id: 3, name: 'dddddd', type: 'text' },
  { id: 4, name: 'eeeeee', type: 'text' },
  { id: 4, name: 'ffffff', type: 'text' },
];

const ret = Object.values(
  users.reduce((prev, c) => {
    const p = prev;
    const key = c.id;
    p[key] = c;
    return p;
  }, {})
);
console.log(ret);

edited Dec 08 '20 at 07:41

answered Dec 08 '20 at 07:34

mr hr

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const ret would be of type unknown[]. How can I make it of type Users[]? – sato desu Dec 08 '20 at 08:04
Why `const p = prev` variable is created? It's not doing anything – adiga Dec 08 '20 at 08:08
@adiga, Assignment to variables declared as function parameters can be misleading and lead to confusing behavior. So, I made it a habit and always code like that. – mr hr Dec 08 '20 at 08:50
@satodesu add type to ret `const ret:Users[]` – mr hr Dec 08 '20 at 08:58

react I want to remove duplicate values in the array

1 Answers1