计算数组中的唯一元素而不进行排序 [英] Count unique elements in array without sorting

问题描述

在JavaScript中，以下内容将查找数组中的元素数。假设数组中至少有一个元素

In JavaScript the following will find the number of elements in the array. Assuming there to be a minimum of one element in the array

arr = ["jam", "beef", "cream", "jam"]
arr.sort();
var count = 1;
var results = "";
for (var i = 0; i < arr.length; i++)
{
    if (arr[i] == arr[i+1])
    {
      count +=1;
    }
    else
    {
        results += arr[i] + " --> " + count + " times\n" ;
        count=1;
    }
}

是否可以在不使用sort（）的情况下执行此操作或者不以任何方式改变数组？我想可能必须重新创建数组，然后可以在新创建的数组上完成排序，但我想知道没有排序的最佳方法是什么。
是的，我是艺术家，而不是程序员，是你的荣誉。

Is it possible to do this without using sort() or without mutating the array in any way? I would imagine that the array would have to be re-created and then sort could be done on the newly created array, but I want to know what's the best way without sorting. And yes, I'm an artist, not a programmer, your honour.

推荐答案

快速执行此操作的方法是将唯一元素复制到对象中。

A quick way to do this is to copy the unique elements into an Object.

var counts = {};
for (var i = 0; i < arr.length; i++) {
    counts[arr[i]] = 1 + (counts[arr[i]] || 0);
}

当此循环完成时，计算 object将拥有数组中每个不同元素的计数。

When this loop is complete the counts object will have the count of each distinct element of the array.

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