I have a simple ngFor loop which also keeps track of the current index. I want to store that index value in an attribute so I can print it. But I can't figure out how this works.

I basically have this:

<ul *ngFor="#item of items; #i = index"> <li>{{item}}</li> </ul>

I want to store the value of #i in the attribute data-index. I tried several methods but none of them worked.

I have a demo here:

How can I store the index value in the data-index attribute?

0

9 Answers

I would use this syntax to set the index value into an attribute of the HTML element:

Angular >= 2

You have to use let to declare the value rather than #.

<ul> <li *ngFor="let item of items; let i = index" [attr.data-index]="i"> {{item}} </li> </ul>

Angular = 1

<ul> <li *ngFor="#item of items; #i = index" [attr.data-index]="i"> {{item}} </li> </ul>

Here is the updated plunkr: .

10

In Angular 5/6/7/8:

<ul> <li *ngFor="let item of items; index as i"> {{i+1}} {{item}} </li> </ul>

In older versions

<ul *ngFor="let item of items; index as i"> <li>{{i+1}} {{item}}</li> </ul>

Angular.io ▸ API ▸ NgForOf

Unit test examples

Another interesting example

4

Just an update to this, Thierry's answer is still correct, but there has been an update to Angular2 with regards to:

<ul *ngFor="let item of items; let i = index" [attr.data-index]="i"> <li>{{item}}</li> </ul>

The #i = index should now be let i = index

EDIT/UPDATE:

The *ngFor should be on the element you're wanting to foreach, so for this example it should be:

<ul> <li *ngFor="let item of items; let i = index" [attr.data-index]="i">{{item}}</li> </ul>

EDIT/UPDATE

Angular 5

<ul> <li *ngFor="let item of items; index as i" [attr.data-index]="i">{{item}}</li> </ul>

EDIIT/UPDATE

Angular 7/8

<ul *ngFor="let item of items; index as i"> <li [attr.data-index]="i">{{item}}</li> </ul>
1

I think its already been answered before, but just a correction if you are populating an unordered list, the *ngFor will come in the element which you want to repeat. So it should be insdide <li>. Also, Angular2 now uses let to declare a variable. 

<ul> <li *ngFor="let item of items; let i = index" [attr.data-index]="i"> {{item}} </li> </ul>
2

The other answers are correct but you can omit the [attr.data-index] altogether and just use 

<ul> <li *ngFor="let item of items; let i = index">{{i + 1}}</li> </ul

Adding this late answer to show a case most people will come across. If you only need to see what is the last item in the list, use the last key word:

<div *ngFor="let item of devcaseFeedback.reviewItems; let last = last"> <divider *ngIf="!last"></divider> </div>

This will add the divider component to every item except the last.

Because of the comment below, I will add the rest of the ngFor exported values that can be aliased to local variables (As are shown in the docs):

  • $implicit: T: The value of the individual items in the iterable (ngForOf).
  • ngForOf: NgIterable: The value of the iterable expression. Useful when the expression is more complex then a property access, for example when using the async pipe (userStreams | async).
  • index: number: The index of the current item in the iterable.
  • count: number: The length of the iterable.
  • first: boolean: True when the item is the first item in the iterable.
  • last: boolean: True when the item is the last item in the iterable.
  • even: boolean: True when the item has an even index in the iterable.
  • odd: boolean: True when the item has an odd index in the iterable.
4

You can use [attr.data-index] directly to save the index to data-index attribute which is available in Angular versions 2 and above.

 <ul*ngFor="let item of items; let i = index" [attr.data-index]="i"> <li>{{item}}</li> </ul>

with laravel pagination

file.component.ts file datasource: any = { data: [] } loadData() { this.service.find(this.params).subscribe((res: any) => { this.datasource = res; }); } html file <tr *ngFor="let item of datasource.data; let i = index"> <th>{{ datasource.from + i }}</th> </tr>

Try this

<div *ngFor="let piece of allPieces; let i=index"> {{i}} // this will give index </div>