按值对对象的属性进行排序并保留值

Question

I have created an array of food names that has duplicate data. By using:

listFoodnames.forEach(x => {
  counts[x] = (counts[x] || 0) + 1;
});

I can count how many times each item exists in the array.

Using:

Object.keys(counts).sort((a, b) => counts[b]-counts[a])

I can sort the items' count from greatest to lowest, however, I lose the actual count that I'd like to keep.

How can I solve this?

 $('document').ready(function() { var listFoodnames = ["Batteries", "Bread", "Milk", "Bread", "Milk", "Milk"] var counts = {}; listFoodnames.forEach(x => { counts[x] = (counts[x] || 0) + 1; }); console.log(counts) //LOGS EACH ITEM AS PROPERTY AND OCCURRENCES AS VALUE var sortedCounts = Object.keys(counts).sort((a, b) => counts[b]-counts[a]) console.log(sortedCounts) //LOSES VALUES }) 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 

Answer 1

Unfortunately, object properties are not guaranteed to be ordered, per the spec. You might try using an array of objects instead.

Also note that reduce is more appropriate than forEach when you're combining items in an array into a single object.

 const listFoodnames = ["Batteries", "Bread", "Milk", "Bread", "Milk", "Milk"]; const counts = Object.values( listFoodnames.reduce((a, foodName) => { if (!a[foodName]) a[foodName] = { foodName, count: 0 }; a[foodName].count++; return a; }, {}) ); counts.sort((a, b) => a.count - b.count); console.log(counts); 

Answer 2

Instead of

var sortedCounts = Object.keys(counts).sort((a, b) => counts[b] - counts[a]);

use

var sortedCounts = Object.entries(counts).sort(([keyA, a], [keyB, b]) => b - a);

Next, you could map each [key, value] entry to a new object:

console.log(sortedCounts.map(([key, value]) => ({[key]: value})));

The result will look like this:

[
  {
    "Milk": 3
  },
  {
    "Bread": 2
  },
  {
    "Batteries": 1
  }
]

Note, that it is impossible to get something like

{
  "Milk": 3,
  "Bread": 2,
  "Batteries": 1
}

to work, since object properties do not have an order.

Answer 3

Everyone who has replied has incorrectly said -> dictionaries are not ordered

This is actually wrong, ES6 made the spec change, and have said dictionary's are ordered. Although before ES6 order was not specified, most browser did even then have an order. The order by the way is insertion order. The order will also work when serialized, eg. JSON.parse / JSON.stringify.

So using this knowledge we can make the result into the format your after, a sorted object.

example below.

 var listFoodnames = ["Batteries", "Bread", "Milk", "Bread", "Milk", "Milk"] var counts = {}; listFoodnames.forEach(x => { counts[x] = (counts[x] || 0) + 1; }); console.log(counts) //LOGS EACH ITEM AS PROPERTY AND OCCURRENCES AS VALUE const sortedCount = Object.entries(counts).sort((a,b) => b[1] - a[1]). reduce((a,v) => (a[v[0]] = v[1], a), {}); console.log(sortedCount);