Angular2 ngFor how to count the number of looping values?

问题

I am using ngFor to loop 8 json objects and I want not only to loop the values but also I want to count the number of looping values and display the number.

For example, if json value is

Content:{
0:"Content1",
1:"Content2",
2:"Content3",
3:"Content4",
4:"Content5",
5:"Content6",
6:"Content7",
7:"Content8"
}

I not only want to display looping values of 'Content', but I also want to count them so that the result could be this below.

1 <- counting
Content1

2
Content2

3
Content3

4
Content4

5
Content5

6
Content6

7
Content7

8
Content8

回答1:

Iterating over array

Regarding the docs: https://angular.io/guide/structural-directives#inside-ngfor and https://angular.io/api/common/NgForOf

Say you have an iterable:

let content = [
  "Content1",
  "Content2",
  "Content3",
  "Content4",
  "Content5",
  "Content6",
  "Content7",
  "Content8"
]

Then you can iterate and count with:

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

Iterating over object properties

If you want to iterate over an object rather than an array of objects, check How to iterate object keys using *ngFor

For the record, you need a custom pipe:

@Pipe({ name: 'keys',  pure: false })
export class KeysPipe implements PipeTransform {
    transform(value: any, args: any[] = null): any {
        return Object.keys(value)//.map(key => value[key]);
    }
}

So that would be

<li *ngFor="let key of objs | keys; let i = index"> ...

Update

From Angular 6.1+, you can use the native KeyValuePipe.

https://blog.angular.io/angular-v6-1-now-available-typescript-2-9-scroll-positioning-and-more-9f1c03007bb6#ff4b

https://angular.io/api/common/KeyValuePipe

For the record:

<li *ngFor="let item of data | keyvalue; let i = index">
  {{i+1}}. {{item.key}} - {{item.value}}
</li>

回答2:

Demo

<ul>
  <li *ngFor="let item of items; let i = index">
    {{i}}. {{item}}
  </li>
</ul>
{{items ? items.length : ''}}

You could just print the length of the items array.

来源：https://stackoverflow.com/questions/43443963/angular2-ngfor-how-to-count-the-number-of-looping-values

标签

json

angular

ngfor