jquery - Javascript，从每个循环中获取唯一值或按 value.id 进行分组

Question

我将值存储在 localStorage 中，并在从 localStorage 检索它们后将它们转换为数组。

我只想返回唯一值或可能将它们分组，这样就不会出现重复项。我使用_下划线作为循环。

$.get_played_songs = function(){
                if (localStorage.getItem("local_songs") === null) { 
                    recent_holder.html('Play some music');
                    } else {
                    var StoredPlays = JSON.parse(localStorage.getItem('local_songs'));  
                    var i=0
                    _.each(StoredPlays, function(value, key){
                        recent_holder.append("<div class='recently_played_jams' data-recently_played_sid='"+value.sid+"'>"+value.title+"</div>");
                    });
                } 
            }

控制台记录“值”返回此值。

Object { title: "Song1", sid: "47" }
Object { title: "Song1", sid: "47" } 
Object { title: "Song1", sid: "47" }
Object { title: "Song12", sid: "47" }
Object { title: "Song2", sid: "47" }
Object { title: "Song2", sid: "47" }
Object { title: "Song2", sid: "47" }

所以我想按 sid 分组。也许一些正则表达式。

Answer 1

_.uniq让您传入一个函数，该函数确定在确定唯一性时要查看的内容，因此如果 sid 使它们具有唯一性:

StoredPlays = _.uniq(StoredPlays, function(play) { return play.sid; });

var StoredPlays = [
  { title: "Song1", sid: "47" },
  { title: "Song1", sid: "47" } ,
  { title: "Song1", sid: "47" },
  { title: "Song12", sid: "47" },
  { title: "Song2", sid: "47" },
  { title: "Song2", sid: "47" },
  { title: "Song2", sid: "47" }
];
StoredPlays = _.uniq(StoredPlays, function(play) { return play.sid; });
snippet.log(JSON.stringify(StoredPlays));

<script src="http://underscorejs.org/underscore.js"></script>
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

或者如果是sid 和 title:

StoredPlays = _.uniq(StoredPlays, function(play) { return play.sid + "/" + play.title; });

var StoredPlays = [
  { title: "Song1", sid: "47" },
  { title: "Song1", sid: "47" } ,
  { title: "Song1", sid: "47" },
  { title: "Song12", sid: "47" },
  { title: "Song2", sid: "47" },
  { title: "Song2", sid: "47" },
  { title: "Song2", sid: "47" }
];
StoredPlays = _.uniq(StoredPlays, function(play) { return play.sid + "/" + play.title; });
snippet.log(JSON.stringify(StoredPlays));

<script src="http://underscorejs.org/underscore.js"></script>
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>