Knockout Observable Array IndexOf method

Question

cityArray.indexOf(data.results[index].City) === -1

How can I use indexOf method for a knockoutObservable array where each item is an object ? cityArray contains objects with a property called City.

You can't. You can use ko.utils.arrayFirst, any other number of existing utility functions, or roll your own loop. Once you var arr = observableArray() you are left with a normal array and can then treat it as any other JavaScript Array. — user2864740
– user2864740, Commented Oct 31, 2013 at 18:56

user2585299 · Accepted Answer · 2013-11-01 14:25:31Z

1

Thanks all for the answers. I was trying to use indexOf method to see if an entry already exists in an observable array. Instead I am now using ko.utils.arrayGetDistinctValues so I no longer have to use indexOf method. But since arrayGetDistinctValues does not work on array of objects, I first copied the values in to a normal array and then used the function on it.

answered Nov 1, 2013 at 14:25

user2585299

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beauXjames · Accepted Answer · 2013-11-01 18:51:27Z

0

cityArray.indexOf(    
    ko.utils.arrayFirst(ko.utils.unwrapObservable(cityArray), function(cityObj) {
        return ko.utils.unwrapObservable(cityObj.City) == 'WallaWalla';
    }
)

The ko.utils.unwrapObservable function will () your object if it needs it and won't if it doesn't. Lightweight...in V2.3 you can just do ko.unwrap just in case you have a fear of too many letters in your js.

The arrayFirst returns the object then the indexOf will pull the comparison of the object and you should get your index...-1 if it doesn't exist...if there are no matches with arrayFirst, you'll get null.

edited Nov 1, 2013 at 18:51

answered Oct 31, 2013 at 23:48

beauXjames

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2 Comments

ebohlman Over a year ago

BTW, ko.unwrap as a shortcut was actually added in 2.3.0

beauXjames Over a year ago

correct...edited above...thanks for pointing that one out...fingers occasionally move quicker than the brain

Dally S · Accepted Answer · 2015-02-19 09:41:55Z

This is how i got my arrayIndexOf to work

var viewModel = function() {
  var self = this;

  self.suggestions = ko.observableArray([]);
  self.filterText = ko.observable('');

  self.filterText.subscribe(function(newValue) {});

  self.suggestionsFilter = ko.computed(function() {
    
    if (self.filterText() === '') {
      return self.suggestions();
    } else {
      return ko.utils.arrayFilter(self.suggestions(), function(item) {

        var filterResults = item.option.toLowerCase().indexOf(self.filterText().toLowerCase()) == 0;
        return filterResults;

      });
    }
  });
};

<div class="col-md-6 postcode-search" id="js-postcode-search-suggestions">
  <input id="name-search" class="form-control" type="search" name="postcode" minlength="1" placeholder="Postcode or Address" data-bind="textInput: filterText" />
  <div class="col-md-12" data-bind="visible: suggestions().length > 1" style="display: none">
    <ul class="suggestions" data-bind="foreach: suggestionsFilter">
      <li class="pad-top-bottom">
        <a href="#">
          <span class="option" data-bind="html: option"></span>
        </a>
      </li>
    </ul>
  </div>
</div>

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