Showing a header 2 element just once using both ngFor and ngIf in Angular

Question

Showing a header 2 element just once using both ngFor and ngIf in Angular

I have an array of words with varying lengths. I am using ng-For to loop through the array and ng-if to display the words based on their lengths, but I am struggling to add titles to separate them.

Expected Outcome:

2 letter words: to, am, as...

3 letter words: the, bee, sin...

And so on...

This is what I have so far:

<div *ngIf="data">
  <h2 class="title">{{data.letters}}</h2>
  <ul class="wordList" *ngFor="let item of data.word">
      <li *ngIf="item.length ==2">{{item}}</li>
      <li *ngIf="item.length ==3">{{item}}</li>
      <li *ngIf="item.length ==4">{{item}}</li>
      <li *ngIf="item.length ==5">{{item}}</li>
      <li *ngIf="item.length ==6">{{item}}</li>
      <li *ngIf="item.length ==7">{{item}}</li>
      <li *ngIf="item.length ==8">{{item}}</li>
      <li *ngIf="item.length ==9">{{item}}</li>
      <li *ngIf="item.length ==10">{{item}}</li>
      <li *ngIf="item.length ==11">{{item}}</li>
      <li *ngIf="item.length ==12">{{item}}</li>
      <li *ngIf="item.length ==13">{{item}}</li>
      <li *ngIf="item.length ==14">{{item}}</li>

    </ul>
</div>

I know I should also use an index to iterate through the word sizes, but I will address that later :)

arrays angular typescript ngfor angular-ng-if

Answer 1

Answer №1

Utilize a Pipe to convert an array of words into an object where the length of the word acts as the key and the words themselves are the values.

@Pipe({ name: 'groupByLengthPipe' })
export class GroupByLengthPipe implements PipeTransform {

    transform(input: []) {
        let map = {};
        input.forEach((e: string) => {
            if (map[e.length]) {
                map[e.length] = map[e.length] + ' ' + e;
            } else {
                map[e.length] = e;
            }
        });
        return map;
    }

}

You can now easily implement this in your template using the syntax below:

<div *ngFor="let word of words | groupByLengthPipe | keyvalue">
    <h2>{{word.key}}</h2> letter words : {{word.value}}
</div>

Answer 2

Utilize a Pipe to convert an array of words into an object where the length of the word acts as the key and the words themselves are the values.

@Pipe({ name: 'groupByLengthPipe' })
export class GroupByLengthPipe implements PipeTransform {

    transform(input: []) {
        let map = {};
        input.forEach((e: string) => {
            if (map[e.length]) {
                map[e.length] = map[e.length] + ' ' + e;
            } else {
                map[e.length] = e;
            }
        });
        return map;
    }

}

You can now easily implement this in your template using the syntax below:

<div *ngFor="let word of words | groupByLengthPipe | keyvalue">
    <h2>{{word.key}}</h2> letter words : {{word.value}}
</div>

Answer 3

Answer №2

It seems like the best approach would be to handle the process of grouping by length within your class and create a structured object to store the data for display purposes. It's important to note that you have a list of groups based on word length, as well as a list of words for each specific group, which means you will need to utilize two nested *ngFor loops.

Within your class:

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnInit {
  private words = ['the', 'to', 'am', 'as', 'bee', 'sin', 'other'];
  groupedByLength: { length: string, words: string[] }[] = [];

  ngOnInit() {
    this.groupByLength();
  }

  private groupByLength() {
    let grouped = {};
    for(let word of this.words) {
      const length = word.length;
      if(!grouped[length]) {
        grouped[length] = [word];
      } else {
        grouped[length].push(word);
      }
    }
    Object.keys(grouped).forEach(key => {
      this.groupedByLength.push({ length: key, words: grouped[key] });
    });
  }
}

In your template:

<div *ngFor="let data of groupedByLength">
    <h2>{{ data.length }} letter words:</h2>
    <ul>
        <li *ngFor="let word of data.words">{{ word }}</li>
    </ul>
</div>

Answer 4

It seems like the best approach would be to handle the process of grouping by length within your class and create a structured object to store the data for display purposes. It's important to note that you have a list of groups based on word length, as well as a list of words for each specific group, which means you will need to utilize two nested *ngFor loops.

Within your class:

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnInit {
  private words = ['the', 'to', 'am', 'as', 'bee', 'sin', 'other'];
  groupedByLength: { length: string, words: string[] }[] = [];

  ngOnInit() {
    this.groupByLength();
  }

  private groupByLength() {
    let grouped = {};
    for(let word of this.words) {
      const length = word.length;
      if(!grouped[length]) {
        grouped[length] = [word];
      } else {
        grouped[length].push(word);
      }
    }
    Object.keys(grouped).forEach(key => {
      this.groupedByLength.push({ length: key, words: grouped[key] });
    });
  }
}

In your template:

<div *ngFor="let data of groupedByLength">
    <h2>{{ data.length }} letter words:</h2>
    <ul>
        <li *ngFor="let word of data.words">{{ word }}</li>
    </ul>
</div>

Showing a header 2 element just once using both ngFor and ngIf in Angular

Answer №1

Answer №2

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Showing a header 2 element just once using both ngFor and ngIf in Angular