shuffle array in ng-repeat angular

Question

I'm creating a quiz and every time I start the quiz I want to shuffle the questions, so that they won't appear in the same order every time.

I have this in my html code:

<div ng-repeat="question in questions | filter:ids | orderBy:randomSort">
    <div id="question">{{question.question}}</div><img id="nextImg" ng-src="../app/img/next.png" ng-click="next()" />
    <img class="quizImg" ng-hide="{{question.image}}==null" ng-src="{{question.image}}" />

    <div class="answer" ng-repeat="answer in question.answers">
        <input type="radio" ng-click="checked(answer)">{{answer.answer}}
    </div>
    <!--input id="nextQuestion" type="button" ng-click="next()" value="{{buttonText}}"-->
</div>

and this in my controller

 lycheeControllers.controller('quizCtrl', ['$scope', '$http', function ($scope, $http) {
    $http.get('json/questions.json').success(function (data) {
        //all questions
        $scope.questions = data;

        $scope.titel = "Check your knowledge about lychees"


        $scope.randomSort = function(question) {
                      return Math.random();
                    };

        //filter for getting answers / question
        $scope.ids = function (question) {
            return question.id == number;
        }

        $scope.find = function (id) {
            if (id == number) {
                return true;
            }
        }


        $scope.next = function () {
            if (!(number == (data.length))) {
                //questionId++;
                number++;
                if (correct == true) {
                    points++;
                }
                //alert(points);
            } else {
                if (!end) {
                    if (correct == true) {
                        points++;
                        end = true;
                    }
                }

                alert("Quiz finished: your total score is: " + points);
            }
            correct = false;
        }

        $scope.checked = function (answer) {
            //alert(answer.answer);

            if (answer.correct == "yes") {
                correct = true;
            } else {
                correct = false;
            }

            //alert(correct);
        }


    });

}])
;

unfortunately this isn't working at all..

Answer 1

Thx to http://bost.ocks.org/mike/shuffle/ use this shuffling function:

Speciality with it is, that the input array stays bindable because the shuffling wont create a new array but instead does the shuffling on the same reference.

// -> Fisher–Yates shuffle algorithm
var shuffleArray = function(array) {
  var m = array.length, t, i;

  // While there remain elements to shuffle
  while (m) {
    // Pick a remaining element…
    i = Math.floor(Math.random() * m--);

    // And swap it with the current element.
    t = array[m];
    array[m] = array[i];
    array[i] = t;
  }

  return array;
}

side note: lodash's _.shuffle(array) does not work either because they are creating a new array which breaks binding (so a shuffled array won't trigger the model to be dirty)

---

To complete the answer to a working solution, following steps should do it:

• copy the function so you can use it inside your controller.
• call it in your $http result callback:

$http.get('json/questions.json').success(function (data) {
  //all questions
  $scope.questions = data;

  shuffleArray($scope.questions);

  ...
}

Answer 2

Use Lodash

_.shuffle(collection)

Answer 3

I used lodash _.shuffle() for showing products in home page randomly. It's very simple to use like below:

In home.component.ts file,

products: IProduct[] = [];

  constructor(private productService: ProductService) {}

  ngOnInit(): void {
    this.productService
      .getProducts()
      .subscribe((prodData: IProductsResponse) => {
        this.products = _.shuffle(prodData.products);
        console.log(this.products);
      });
  }

In home.component.html file,

<div class="col-md-4 col-sm-6" *ngFor="let product of products let idx = index">
            <div class="card my-2" *ngIf="idx <= 8">
                <img
                  [src]="product.image"
                  alt="{{ product.title }}"
                  width="200px"
                  height="300px"
                  class="card-img-top"
                  style="cursor: pointer"
                  (click)="selectProduct(product._id)"
                />
                <div class="card-header">
                  <div class="card-title">
                    <p>{{ product.title.substr(0, 50) | uppercase }}</p>
                  </div>
                </div>
         </div>
 </div>