javascript - 检查一个项目是否存在于 observableArray 中

Question

为什么检查重复的 Artist 总是返回 false？

查看此 JSFiddle用于可运行的演示。

knockout 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

您正在检查它是否大于零。这意味着如果它位于位置 0，artistExists 将被设置为 false，因为零不大于零。

不过，这仍然行不通。数组中填充的是Artist对象，不能正常搜索，因为你搜索的对象和数组中的对象不一样，即使它们有相同的name 值。