如何将 javascript 字符串数组减少为唯一值但保持重复数的计数？

Question

I have an array with a number of strings, like this one:

["e", "e", "e", "e", "a", "e", "e", "a", "e", "e", "e", "e", "e", "o", "a", "e", "r", "e", "e", "e", "o", "e", "u"]

Now I want to reduce this array so it only contains unique strings. At the same time I want to keep count of the number of duplicates and (preferably) calculate a percentage that shows number of duplicates divided by the total number of strings.

I'm thinking an end result that looks something like this:

[
    {
        letter: "e",
        duplicates: 16,
        percentage: 0.695652173913043
    },
    {
        letter: "a",
        duplicates: 3,
        percentage: 0.130434782608696
    },
    {
        letter: "o",
        duplicates: 2,
        percentage: 0.08695652173913
    },
    {
        letter: "r"
        duplicates: 1,
        percentage: 0.043478260869565
    },
    {
        letter: "u",
        duplicates: 1,
        percentage: 0.043478260869565
    }
]

How would I go about making this transformation in JavaScript/ES6?

Answer 1

 let array = ["e", "e", "e", "e", "a", "e", "e", "a", "e", "e", "e", "e", "e", "o", "a", "e", "r", "e", "e", "e", "o", "e", "u"] let result = [...new Set(array)].map(e =>({letter:e, duplicates:array.filter(n => n===e).length, percentage:array.filter(n => n===e).length/array.length})) console.log(result)

Answer 2

This is possible by using Array#from , Array#reduce , Map , Array#map , and destructuring .

The reduce allows to regroup and count letters and their occurrence. Once they've been organized properly you can then proceed to map through all the results and calculate the percentage.

 const data = ["e", "e", "e", "e", "a", "e", "e", "a", "e", "e", "e", "e", "e", "o", "a", "e", "r", "e", "e", "e", "o", "e", "u"]; const res = Array.from(data.reduce((acc, cur) => acc.set(cur, (acc.get(cur)||0) + 1), new Map())).map(([letter, duplicates]) => ({letter, duplicates, percentage: duplicates / data.length})); console.log(res);