javascript 排序和重映射数组

Question

我正在使用以下代码（由JQuery Javascript Sort Array by Highest Count 提供）对字符串列表从最高计数到最低计数进行排序：

var items = {}, sortableItems = [], i, len, element, listOfStrings; 

    listOfStrings = JSON.parse(the_chems);


for (i = 0, len = listOfStrings.length; i < len; i += 1) 
    {
        if (items.hasOwnProperty(listOfStrings[i])) {
            items[listOfStrings[i]] += 1;
        } else {
            items[listOfStrings[i]] = 1;
        }
    }

for (element in items) 
    {
        if (items.hasOwnProperty(element)) {
            sortableItems.push([element, items[element]]);
        }
    }

sortableItems.sort(function (first, second) 
    {
        return second[1] - first[1];
    });

代替这种类型的数组输入

["red", "red", "red", "blue", "blue"]

返回

[ [ "red", 3 ], [ "blue", 2 ] ]

我想使用像

这样的数组

[["red","apple"], ["red","chilli"], ["red","melon"], ["blue","ocean"], ["blue","eyes"]]

然后返回

[["red", 3, ["apple","chilli","melon"]], ["blue", 2, ["blue","ocean"]]

Answer 1

您可以使用哈希表并将结果收集到一个数组中。

var array = [["red", "apple"], ["red", "chilli"], ["red", "melon"], ["blue", "ocean"], ["blue", "eyes"]],
    hash = Object.create(null),
    result = [];

array.forEach(function (a) {
    if (!hash[a[0]]) {
        hash[a[0]] = [a[0], 0, []];
        result.push(hash[a[0]]);
    }
    hash[a[0]][1]++;
    hash[a[0]][2].push(a[1]);
});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

您可以使用地图和一些很酷的解构：

var hash = new Map(), result = [];

input.forEach(([color,fruit]) => {
 if(hash.has(color)){
  var arr = hash.get(color);
  arr[1]++;
  arr[2].push(fruit);
 }else{
  var tmp = [color,1,[fruit]];
  hash.set(color,tmp);
  result.push(tmp);
 }
});

Try it out （提示：这对于对象来说是一个很好的用例......）

---

速度较慢，但​​可能更具可读性：

var hash = new Map();

input.forEach(([color,fruit])=>{
 if(hash.has(color)){
  hash.get(color).push(fruit);
 }else{
  hash.set(color,[fruit]);
 }
})

var result = [...hash.entries()].map(([color,fruits])=>[color,fruits.length,fruits]);

Answer 3

为什么不创建一个像这样有用的数据结构：

{
  red:["apple","chili","melon"],
  blue:["ocean","eyes"]
}

用一个循环完成，没有多余的哈希表：

var arr = [["red","apple"], ["red","chilli"], ["red","melon"], ["blue","ocean"], ["blue","eyes"]];
arr.reduce(function(c,element) {
    if(!c[element[0]]) {
        c[element[0]] = [];
    }
    c[element[0]].push(element[1]);
    return c;
},{});

对于那些不关心可读代码的人：

arr.reduce(function(c,element) {
    return (c[element[0]] ? c[element[0]].push(element[1]) : c[element[0]] = [element[1]]) && c;
},{});

Answer 4

没有地图也可以...

function groupAndSort(items){
    var output = []
    for(var i=0;i<items.length;i++){
        var exists = false;
        for(var u=0;u<output.length;u++){
            if(output[u][0]==items[i][0]){
                output[u][1]++
                output[u][2].push(items[i][1])
                exists = true
                break
            }
        }
        if(!exists)
            output.push([items[i][0],1,[items[i][1]]])
    }
    output.sort(function (first, second){
        return second[1] - first[1];
    });
    return output
}

Answer 5

您可以使用Array.reduce 重构数组。

const arr = [["red","apple"], ["red","chilli"], ["red","melon"], ["blue","ocean"], ["blue","eyes"]];

const newArr = arr.reduce((acc , curr) => {
  let flag = false;
  acc.forEach(a => {
    if(a[0] === curr[0]) {
      a[1]++;
      a[2].push(curr[1]);
      flag = true;
    }
  });
  if(!flag) {
    let newArr = [curr[0], 1, [curr[1]]];
    acc.push(newArr);
  }
  return acc;
}, []);

console.log(newArr);

Answer 6

这是另一个解决方案。首先，该函数创建每种颜色的简单计数。从那里，我们遍历对象并过滤/映射相关项目，并推送我们最终所需的输出。

const testArray = [["red","apple"], ["red","chilli"], ["red","melon"], ["blue","ocean"], ["blue","eyes"]]

function modifyArray(arr) {
  let colorCount = arr.reduce((allColors, color) => {
    if (color[0] in allColors) {
      allColors[color[0]]++
	}
	else {
	  allColors[color[0]] = 1
	}
	return allColors
  }, {})

  let newArr = [];

  for (var key in colorCount) {
    let coloredItems = arr.filter(val => val[0] === key).map(val => val[1])
    newArr.push([key, colorCount[key], coloredItems])
  }

  return newArr;
}

console.log(modifyArray(testArray))