检查observableArray中是否存在某个项目

Question

为什么重复检查Artist总是返回false？

有关可运行的演示,请参阅此JSFiddle.

淘汰赛代码

$(function() {

  function Artist(name) {
    this.name = name;
  }

  function ViewModel() {
    var self = this;
    self.favoriteArtists = ko.observableArray([]);
    self.artistToAdd = ko.observableArray("");
    self.addArtist = function () {
      var newFavoriteArtist = new Artist(self.artistToAdd());
      console.log("New Favorite Artist: " + newFavoriteArtist.name);
      var artistExists = self.favoriteArtists.indexOf(newFavoriteArtist) > 0;
      console.log("Artist Exists: " + artistExists);
      if(!artistExists) {
          self.favoriteArtists.push(newFavoriteArtist);
          console.log("A new artist has been added:" + self.artistToAdd());
      } else {
        console.log("Artist already in favorites.");
      }
    };
  }  
  ko.applyBindings(new ViewModel());
});

HTML

<h1>Favorite Artists</h1>
<p>Currently, your favorite artists include:</p>
<ul data-bind="foreach: favoriteArtists">
    <li> <span data-bind="text: name"></span>
    </li>
</ul>
<p>Enter the name of a new artist:</p>
<input data-bind="value: artistToAdd" />
<button data-bind="click: addArtist">Add</button>

Answer 1

您的支票应该是以下之一:

self.favoriteArtists.indexOf(newFavoriteArtist) >= 0

self.favoriteArtists.indexOf(newFavoriteArtist) != -1

self.favoriteArtists.indexOf(newFavoriteArtist) > -1

你正在检查它是否大于零.这意味着如果它在位置0,artistExists将被设置为false因为零不大于零.

但这仍然不起作用.数组中填充的Artist对象无法正常搜索,因为您搜索的对象与数组中的对象不同,即使它们具有相同的name值.

Answer 2

不确定,但是self.favoriteArtists.indexOf(newFavoriteArtist)> 0; 看起来有点奇怪,我期待那里有-1.如果你经常添加相同的艺术家,它会一直认为它不存在.

并且你不断创建新的对象,这些对象不在列表中.(复杂)对象默认情况下彼此不相等.