在 JavaScript 中有效地将 2D 数组转换为删除重复项的对象

Question

例如，如果有以下二维数组（排列为 [[key, value], [key, value]]）：

var input_array = [
  ["one", "stuff"], 
  ["two", "things"], 
  ["two", "more things"], 
  ["three", "stuff"], 
  ["one", "something"], 
  ["one", "stuff"], 
  ["two", "more things"], 
  ["three", "more stuff"]
]

使用 ES5/6 必须提供的（与带有计数器的 for 循环相反）创建输出对象的最小且有效的方法是什么按字母顺序排列的值:

var output_obj = {
  "one": ["something", "stuff"],
  "two": ["more things", "things"],
  "three": ["more stuff", "stuff"]
}

Answer 1

您无法订购对象，但是...

const input_array = [
  ["one", "stuff"], 
  ["two", "things"], 
  ["two", "more things"], 
  ["three", "stuff"], 
  ["one", "something"], 
  ["one", "stuff"], 
  ["two", "more things"], 
  ["three", "more stuff"]
];
let obj = {}, p, v;
for(let a of input_array){
  p = a[0]; v = a[1];
  if(obj.hasOwnProperty(p)){
    if(obj[p].indexOf(v) === -1)obj[p].push(v);
  }
  else{
    obj[p] = [v];
  }
}
for(let i in obj){
  obj[i].sort();
}
console.log(obj);

Answer 2

也许你可以先创建字符串到列表（数组）的映射，然后再对它们进行排序。

const fn = (arr) => {
    const results = arr.reduce((acc, curr) => {
    acc[curr[0]] = acc[curr[0]] || [];
    if (!acc[curr[0]].includes(curr[1])) {
        acc[curr[0]].push(curr[1]);
    }
    return acc;
    }, {});
  Object.values(results).forEach(vals => vals.sort());
  return results;
}

console.log(fn([
  ["one", "stuff"], 
  ["two", "things"], 
  ["two", "more things"], 
  ["three", "stuff"], 
  ["one", "something"], 
  ["one", "stuff"], 
  ["two", "more things"], 
  ["three", "more stuff"]
]));

Answer 3

一种有效的 ES6 消除重复项的方法是使用 Set.

const input_array = [
  ['one', 'stuff'],
  ['two', 'things'],
  ['two', 'more things'],
  ['three', 'stuff'],
  ['one', 'something'],
  ['one', 'stuff'],
  ['two', 'more things'],
  ['three', 'more stuff']
];

// create object containing sets
const output_obj = input_array
  .reduce((sets, [key, val]) => {
    sets[key] = sets[key] || new Set();
    sets[key].add(val);
    return sets;
  }, {});

// convert each set to a sorted array
Object.entries(output_obj)
  .forEach(([key, set]) => {
    output_obj[key] = [...set].sort();
  });

console.log('output_obj:', output_obj);

Answer 4

这可以像使用 logical nullish assignment (??=), adding elements to a Set() to handle duplicates, and then iterating the resulting Object.keys() to convert the Sets to arrays using spread syntax 的单行 reduce 一样简洁，同时还对它们进行排序。

const input = [["one", "stuff"], ["two", "things"], ["two", "more things"], ["three", "stuff"], ["one", "something"], ["one", "stuff"], ["two", "more things"], ["three", "more stuff"]];

const
  output = input.reduce((a, [k, v]) => ((a[k] ??= new Set()).add(v), a), {});
Object.keys(output).forEach(k => output[k] = [...output[k]].sort());

console.log(output)

或者如果您需要避免 compatibility...

的逻辑空赋值

const input = [["one", "stuff"], ["two", "things"], ["two", "more things"], ["three", "stuff"], ["one", "something"], ["one", "stuff"], ["two", "more things"], ["three", "more stuff"]];

const
  output = input.reduce((a, [k, v]) => ((a[k] = a[k] || new Set()).add(v), a), {});
Object.keys(output).forEach(k => output[k] = [...output[k]].sort());

console.log(output)

在 JavaScript 中有效地将 2D 数组转换为删除重复项的对象

Efficiently converting 2D array to an object erasing duplicates in JavaScript

javascript

arrays

object

ecmascript-5

ecmascript-6