[Javascript] Advanced Reduce: Flatten, Flatmap and ReduceRight

Learn a few advanced reduction patterns: flatten allows you to merge a set of arrays into a single array, the dreaded flatmap allows you to convert an array of objects into an array of arrays which then get flattened, and reduceRight allows you to invert the order in which your reducer is applied to your input values.

 

Flatten

var data = [[1,2,3], [4,5,6], [7,8,9]];
var flatData = data.reduce( (acc, value) => {
  return acc.concat(value);
}, []);

console.log(flatData); //[1, 2, 3, 4, 5, 6, 7, 8, 9]

 

Flatmap 

复制代码
var input = [
  {
    title: "Batman Begins",
    year: 2005,
    cast: [
      "Christian Bale",
      "Michael Caine",
      "Liam Neeson",
      "Katie Holmes",
      "Gary Oldman",
      "Cillian Murphy"
    ]
  },
  {
    title: "The Dark Knight",
    year: 2008,
    cast: [
      "Christian Bale",
      "Heath Ledger",
      "Aaron Eckhart",
      "Michael Caine",
      "Maggie Gyllenhal",
      "Gary Oldman",
      "Morgan Freeman"
    ]
  },
  {
    title: "The Dark Knight Rises",
    year: 2012,
    cast: [
      "Christian Bale",
      "Gary Oldman",
      "Tom Hardy",
      "Joseph Gordon-Levitt",
      "Anne Hathaway",
      "Marion Cotillard",
      "Morgan Freeman",
      "Michael Caine"
    ]
  }
];

var flatMapInput = input.reduce((acc, value)=>{
  value.cast.forEach((star)=>{
    if(acc.indexOf(star) === -1){
      acc.push(star);
    };
  });
  
  return acc;
}, []);


//["Christian Bale", "Michael Caine", "Liam Neeson", "Katie Holmes", "Gary Oldman", "Cillian Murphy", "Heath Ledger", "Aaron Eckhart", "Maggie Gyllenhal", "Morgan Freeman", "Tom Hardy", "Joseph Gordon-Levitt", "Anne Hathaway", "Marion Cotillard"]
复制代码

 

ReduceRight

var countDown = [1,2,3,4,"5"];

var str = countDown.reduceRight((acc, value)=>{
  return acc + value;
}, "");

console.log(str); //"54321"

 

posted @   Zhentiw  阅读(378)  评论(0编辑  收藏  举报
(评论功能已被禁用)
编辑推荐:
· SQL Server 2025 AI相关能力初探
· Linux系列:如何用 C#调用 C方法造成内存泄露
· AI与.NET技术实操系列(二):开始使用ML.NET
· 记一次.NET内存居高不下排查解决与启示
· 探究高空视频全景AR技术的实现原理
阅读排行:
· 阿里最新开源QwQ-32B,效果媲美deepseek-r1满血版,部署成本又又又降低了!
· Manus重磅发布:全球首款通用AI代理技术深度解析与实战指南
· 开源Multi-agent AI智能体框架aevatar.ai,欢迎大家贡献代码
· 被坑几百块钱后,我竟然真的恢复了删除的微信聊天记录!
· AI技术革命,工作效率10个最佳AI工具
历史上的今天:
2014-12-17 [Javascript] Function scope
2014-12-17 [AngularJS] ui-router: named views
2014-12-17 [AngularJS] ui-router: Abstract States
点击右上角即可分享
微信分享提示