Unable to retrieve a random element from an array in Angular 10

Question

Unable to retrieve a random element from an array in Angular 10

I'm attempting to shuffle items (cards that have English words) from a flashCards array, so that each card can appear randomly when the user reloads the page. I tried using the Math.floor(Math.random()) function, but it's not working. How can I randomly display cards from an array of cards?

home.page.html:

<ion-content padding>
     <app-flash-card *ngFor="let card of flashCards" [ngClass]="randomize()">
        <div class="flash-card-front">{{card.front}}</div>

        <div class="flash-card-back">{{card.back}}</div>
     </app-flash-card>  
</ion-content>

home.page.ts:

export class HomePage {

    flashCards: any;
  
  constructor(public navCtrl: NavController) {
        this.flashCards = [
            {back: 'accreditation', front: 'official approval'},
            {back: 'AIDA', front: 'Attention, Interest, Desire, Action (Model for advertising effectiveness)'},
            {back: 'airtime', front: 'broadcasting time'},
            {back: 'ambient noise', front: 'background noise'},
            {back: 'ambitious', front: 'ambitious, driven'}
        ];
    };
    randomize(){    
        var index=Math.floor(Math.random()*this.flashCards.length);
        return this.flashCards[index];
    }
}

angular typescript ionic-framework

Answer 1

Answer №1

Here's a comprehensive solution: Following the suggestions from the comments, you can utilize the existing shuffle function by accessing it either in the constructor or the ngOnInit function (following Angular conventions). I stored your flashCards in a new var and assigned it to this.flashCards after shuffling (which is later referenced in your HTML). This ensures that the array is shuffled before being displayed:

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

export class HomePage implements OnInit {

    flashCards: any;
  
    constructor(public navCtrl: NavController) { }

    ngOnInit(): void {
        var flashCards = [
            {back: 'accreditation', front: 'offizielle Zustimmung'},
            {back: 'AIDA', front: 'Attention, Interest, Desire, Action (Aufmerksamkeit, Interresse, Wunsch, Handlung)-> Modell zur Werbewirkung'},
            {back: 'airtime', front: 'Sendezeit'},
            {back: 'ambient noise', front: 'Umgebungsgeräusch'},
            {back: 'ambitious', front: 'ehrgeizig,strebsam'}
        ];
        this.flashCards = this.shuffle(flashCards)
    }

    shuffle (array) {
        var currentIndex = array.length, temporaryValue, randomIndex;

        // While there remain elements to shuffle...
        while (0 !== currentIndex) {

            // Pick a remaining element...
            randomIndex = Math.floor(Math.random() * currentIndex);
            currentIndex -= 1;

            // And swap it with the current element.
            temporaryValue = array[currentIndex];
            array[currentIndex] = array[randomIndex];
            array[randomIndex] = temporaryValue;
        }

        return array;
    }
}

Furthermore, you can remove the [ngClass] and simply structure it like this:

<ion-content padding>
     <app-flash-card *ngFor="let card of flashCards">
        <div class="flash-card-front">{{card.front}}</div>

        <div class="flash-card-back">{{card.back}}</div>
     </app-flash-card>  
</ion-content>

The shuffling is handled in ngOnInit and using [ngClass] would not be the appropriate approach.

Best of luck!

Answer 2

Here's a comprehensive solution: Following the suggestions from the comments, you can utilize the existing shuffle function by accessing it either in the constructor or the ngOnInit function (following Angular conventions). I stored your flashCards in a new var and assigned it to this.flashCards after shuffling (which is later referenced in your HTML). This ensures that the array is shuffled before being displayed:

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

export class HomePage implements OnInit {

    flashCards: any;
  
    constructor(public navCtrl: NavController) { }

    ngOnInit(): void {
        var flashCards = [
            {back: 'accreditation', front: 'offizielle Zustimmung'},
            {back: 'AIDA', front: 'Attention, Interest, Desire, Action (Aufmerksamkeit, Interresse, Wunsch, Handlung)-> Modell zur Werbewirkung'},
            {back: 'airtime', front: 'Sendezeit'},
            {back: 'ambient noise', front: 'Umgebungsgeräusch'},
            {back: 'ambitious', front: 'ehrgeizig,strebsam'}
        ];
        this.flashCards = this.shuffle(flashCards)
    }

    shuffle (array) {
        var currentIndex = array.length, temporaryValue, randomIndex;

        // While there remain elements to shuffle...
        while (0 !== currentIndex) {

            // Pick a remaining element...
            randomIndex = Math.floor(Math.random() * currentIndex);
            currentIndex -= 1;

            // And swap it with the current element.
            temporaryValue = array[currentIndex];
            array[currentIndex] = array[randomIndex];
            array[randomIndex] = temporaryValue;
        }

        return array;
    }
}

Furthermore, you can remove the [ngClass] and simply structure it like this:

<ion-content padding>
     <app-flash-card *ngFor="let card of flashCards">
        <div class="flash-card-front">{{card.front}}</div>

        <div class="flash-card-back">{{card.back}}</div>
     </app-flash-card>  
</ion-content>

The shuffling is handled in ngOnInit and using [ngClass] would not be the appropriate approach.

Best of luck!

Unable to retrieve a random element from an array in Angular 10

Answer №1

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