Tips on pairing elements from a ngFor processed list with another list using ngIf

Question

Tips on pairing elements from a ngFor processed list with another list using ngIf

If we have a list such as the one shown below:

elements = [
  { id: 1,
    name: "one"
  },
  { id: 3,
    name: "three"
  },
  { id: 5,
    name: "five"
  },
  { id: 6,
    name: "six"
  },
];

lists = [
  { id: 5,
    name: "five"
  },
  {
    id: 9,
    name: "nine"
  },
];

I am trying to make sure that only items with matching ids from 'elements' and 'lists' are displayed when using ngFor and ngIf directives. However, I am unsure of the correct syntax to achieve this.

<div *ngFor="let element of elements">
  <p *ngIf = "lists.some(list => list.id === element.id)">
    {{ element.name }}
  </p>
</div>

javascript angular typescript

Answer 1

Answer №1

If you want to determine if a specific item exists in an array, you can utilize the Array#some method.

<p *ngIf="lists.some(e => e.id === item.id)">

The some method will return true when it finds an element in the lists array with the same id value as the item being checked.

Answer 2

If you want to determine if a specific item exists in an array, you can utilize the Array#some method.

<p *ngIf="lists.some(e => e.id === item.id)">

The some method will return true when it finds an element in the lists array with the same id value as the item being checked.

Answer 3

Answer №2

If you want to streamline the filtering process for your items, consider implementing a custom pipe within the *ngFor directive.

Here is an example of how you can achieve this:

<div *ngFor="let item of items | customFilter:lists">
  <p>
    {{ item.name }}
  <p>
<div>

Now, let's create the custom pipe:

@Pipe({name: 'customFilter'})
export class CustomFilterPipe implements PipeTransform {
  transform(items: object[], lists: object[]): object[] {
    return items.filter(item => {
      lists.some(e => e.id === item.id)
    });
  }
}

Answer 4

If you want to streamline the filtering process for your items, consider implementing a custom pipe within the *ngFor directive.

Here is an example of how you can achieve this:

<div *ngFor="let item of items | customFilter:lists">
  <p>
    {{ item.name }}
  <p>
<div>

Now, let's create the custom pipe:

@Pipe({name: 'customFilter'})
export class CustomFilterPipe implements PipeTransform {
  transform(items: object[], lists: object[]): object[] {
    return items.filter(item => {
      lists.some(e => e.id === item.id)
    });
  }
}

Tips on pairing elements from a ngFor processed list with another list using ngIf

Answer №1

Answer №2

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