JavaScript for in - 从主对象获取、合并和处理数组

Question

我有一个具有以下结构的对象:

var PostsData = [
                {
                    postId: 1,
                    postTitle: 'Cuba slam U.S. on human rights',
                    postExcerpt: 'Washington (CNN)U.S. and Cuban officials began a historic round of talks on Wednesday to bridge a 50-year rift in diplomatic relations, but just a day later, the Cuban delegation slammed the United States on its human rights track record.',
                    postTags: ['cuba', 'human rights', 'diplomatics', 'world']
                },
                {
                    postId: 2,
                    postTitle: 'YouTube stars interview Obama',
                    postExcerpt: "In his continuing effort to connect to a younger audience (like the time he went on 'Between Two Ferns'), President Barack Obama sat down with, and took questions, from three YouTube stars: GloZell Green (3 million followers), Bethany Mota (8 million followers) and half of the vlogbrothers (2.4 million followers).",
                    postTags: ['YouTube', 'interview', 'Obama', 'president']
                },
                // etc...
            ];

我需要从该对象的每个“postTags”数组中获取所有值(合并所有数组)，然后我需要从中删除所有重复值。因此，我需要一次提取所有具有非重复值的标签。我正在研究 for 循环，但它变得非常复杂，我的知识有时会耗尽。你能给我一些建议吗？提前致谢!

(我在 Angularjs 环境中使用它，我正在尝试嵌套的 ng-repeats，我希望我能想出一些简单但运气不好的东西。)

Answer 1

您可以使用 Array.prototype.reduce 和 Array.protoype.forEach 构建一个唯一标记值数组:

var uniqueTags = PostsData.reduce(function(allTags, post) {  
  post.postTags.forEach(function(tag) { 
    if(allPosts.indexOf(tag) === - 1) {
      allTags.push(tag)
    }
  }); 
  return allTags; 
}, []);

或者，如果您可以使用 underscore.js 或 lo-dash:

_.chain(PostsData).pluck('postTags').flatten().uniq().value()