基于另一个数组的对象的打字稿过滤器数组

Question

I have an array of objects like given below

  readonly allItems = [
    {
      id: 0,
      title: "Item 0",
      belongsTo: 'admin'
    },
    {
      id: 1,
      title: "Item 1",
      belongsTo: 'user'
    },
    {
      id: 2,
      title: "Item 2",
      belongsTo: 'all'
    },
    {
      id: 3,
      title: "Item 3",
      belongsTo: 'user'
    },
    {
      id: 4,
      title: "Item 4",
      belongsTo: 'all'
    }
  ];

And I have an array of numbers like given below

let selItems = [0,2,4];

What I'm trying to do is, filter the allItems array based on selItems array For doing that, I wrote the following code, which is obviously wrong.

  for(let i=0; i< this.allItems.length; i++){
      if(selItems.includes(this.allItems[i].id)){
        tempMenu.push(this.allItems[i]);
      }
      console.log(tempMenu);
    }

I'm getting the following as output

[{
      id: 0,
      title: "Item 0",
      belongsTo: 'admin'
}]

The result I'm expecting is like this:

  [
    {
      id: 0,
      title: "Item 0",
      belongsTo: 'admin'
    },
    {
      id: 2,
      title: "Item 2",
      belongsTo: 'all'
    },
    {
      id: 4,
      title: "Item 4",
      belongsTo: 'all'
    }
  ]

Can anyone show me the right way to do this? Thanks!

Answer 1

You might use .map instead:

 const allItems = [{ id: 0, title: "Item 0", belongsTo: 'admin' }, { id: 1, title: "Item 1", belongsTo: 'user' }, { id: 2, title: "Item 2", belongsTo: 'all' }, { id: 3, title: "Item 3", belongsTo: 'user' }, { id: 4, title: "Item 4", belongsTo: 'all' } ]; const selItems = [0, 2, 4]; const output = selItems.map(num => allItems.find(({ id }) => id === num)); console.log(output); 

To reduce computational complexity to O(N) instead of O(N^2) , you can transform it into an object indexed by id first:

 const allItems = [{ id: 0, title: "Item 0", belongsTo: 'admin' }, { id: 1, title: "Item 1", belongsTo: 'user' }, { id: 2, title: "Item 2", belongsTo: 'all' }, { id: 3, title: "Item 3", belongsTo: 'user' }, { id: 4, title: "Item 4", belongsTo: 'all' } ]; const selItems = [0, 2, 4]; const allItemsById = allItems.reduce((a, item) => { a[item.id] = item; return a; }, {}); const output = selItems.map(num => allItemsById[num]); console.log(output); 

Or with filter :

 const allItems = [{ id: 0, title: "Item 0", belongsTo: 'admin' }, { id: 1, title: "Item 1", belongsTo: 'user' }, { id: 2, title: "Item 2", belongsTo: 'all' }, { id: 3, title: "Item 3", belongsTo: 'user' }, { id: 4, title: "Item 4", belongsTo: 'all' } ]; const selItemsSet = new Set([0, 2, 4]); const output = allItems.filter(({ id }) => selItemsSet.has(id)); console.log(output);