Angular JS ng-repeat choose random grouping from array?

Question

I have an array of 6 objects.

I have a list with an ng-repeat where I want to display 3 unique items from those 6 items.

One each refresh, it might pull 3 different items, but it's ok if it does not, the only thing is that the 3 cannot have duplicates amongst themselves.

As an example, if the array is [red, yellow, blue, green, purple, cyan, fuchsia] then on refresh I could get:

red,blue,green
purple,blue,yellow
fuchsia,green,red

etc. As you can see, I don't care that blue came up twice in a row there, but I must never get red, blue, blue.

I have this code:

<ul class="ch-grid">
  <li ng-repeat="user in home.testimonials|orderBy:random|limitTo: 3">
    <div class="ch-item ch-img-1" style="background-image: url(assets/images/{{user.image}})">
      <div class="ch-info">
        <h3>{{user.quote}}</h3>
      </div>
    </div>
    <h3 class="name">{{user.name}}</h3>
    <p class="title">{{user.title}}</p>
  </li>
</ul>

and them in my controller:

_this.random = function () {
  return 0.5 - Math.random();
};

_this.testimonials = [
  {
    name: 'Sara Conklin',
    title: 'SMB/SendPro UX Architect',
    image: 'sara-conklin.jpg',
    quote: 'Instead of inventing original solutions, we can leverage DS guidelines and components, save time, ensure great UX and promote consistency. '},
  {
    name: 'Jenn Church',
    title: 'User Experience Designer',
    image: 'jenn-church.jpg',
    quote: 'The Design System has been a great tool in rapid prototyping, allowing me to get modern, on-brand interfaces put together quickly without having to start from scratch.'},
  {
    name: 'Peter Leeds',
    title: 'Global Creative and Brand Activation',
    image: 'peter-leeds.jpg',
    quote: 'Design System provides the unified, consistent look needed to preserve and reinforce the integrity of our brand.”'},
  {
    name: 'Marcy Goode',
    title: 'Digital Marketing, Self Service & Content Management Leader',
    image: 'marcy-goode.jpg',
    quote: 'Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iusto, ipsam, mollitia in vitae nemo aliquam.'},
  {
    name: 'Clarence Hempfield',
    title: 'Spectrum Spatial Analyst Product Manager',
    image: 'clarence.jpg',
    quote: 'Design System isn’t just about the interface. It’s about understanding how people are expecting to interact with your technology.'},
  {
    name: 'Aaron Videtto',
    title: 'SendSuite Tracking Online Product Manager',
    image: 'aaron.jpg',
    quote: 'Customers of SendSuite Tracking Online have been up and running within 10-15 minutes. We were able to do this because of the Design System.'}
];

But it is not limiting to 3, I get dozens.

OK, trying the filter route as suggested by @csschapker:

    (function () {
  'use strict';

  angular.module('pb.ds.home').filter('getThree', function () {
    return function (array) {
      var copy = angular.copy(array);
      var sample = [];
      while (sample.length < 3) {
        var randomIndex = Math.floor(Math.random() * (copy.length));
        sample.push(copy[randomIndex]);
      }
      return sample;
    };
  });
})();

and

    <ul class="ch-grid">
  <li ng-repeat="user in home.testimonials|filter:getThree">
    <div class="ch-item ch-img-1" style="background-image: url(assets/images/{{user.image}})">
      <div class="ch-info">
        <h3>{{user.quote}}</h3>
      </div>
    </div>
    <h3 class="name">{{user.name}}</h3>
    <p class="title">{{user.title}}</p>
  </li>
</ul>

This simply prints out all 6. I must be missing something.

Answer 1

User random and limitTo filters.

<p ng-repeat="i in list|orderBy:random|limitTo:3">{{i}}</p>

Answer 2

This answer is a good start for a filter but there are problems with it (see the comments). I would delete the answer but the comments may be useful to someone in the future. My new answer is a better way to solve this problem for now.

You can use a custom filter:

.filter('randomSample', function() {
    return function(array, length) {
        var copy = angular.copy(array);
        var sample = [];
        while(sample.length < length) {
            var randomIndex = Math.floor(Math.random() * (copy.length));
            sample.push(copy.splice(randomIndex, 1)[0]);
        }
        return sample;
    };
})

Use it like:

<li ng-repeat="item in array | randomSample:3">{{ item }}</li>

Here's an example on plnkr: http://plnkr.co/edit/NgsQlvgrCD7vLXnBC7q1?p=preview

Answer 3

After many attempts, it looks like it is better to get the random values in your controller after the array is populated. Like so:

_this.sample = [];
var copy = angular.copy(_this.testimonials);
while(_this.sample.length < 3) {
    var randomIndex = Math.floor(Math.random() * (copy.length));
    _this.sample.push(copy.splice(randomIndex, 1)[0]);
}

Then just ng-repeat="user in home.sample"