如何仅使用数组方法在JavaScript中统计数组中的重复值

Hey there! 😊

It’s hard to jump in and fix that ? spot without seeing your current code and knowing exactly what you’re trying to build—like, are you working with arrays, strings, hunting for duplicates, grabbing a specific value, or something else? But since you’ve got super strict rules to follow (only length, toString(), sort(), indexOf() allowed, no loops or conditionals), I can throw out a couple of valid example tricks that fit these constraints to get you thinking:

Example 1: Detect if an array has duplicates #

Since we can’t loop, we can use sort() to group duplicates next to each other, then turn the array into a string and check if any repeated values show up back-to-back with indexOf():

const myArray = [3, 1, 4, 3, 2];
const sortedStr = myArray.sort().toString();
const hasDuplicates = sortedStr.indexOf(sortedStr.charAt(0) + ',' + sortedStr.charAt(0)) !== -1 
  || sortedStr.indexOf(',' + sortedStr.charAt(sortedStr.length-1) + ',' + sortedStr.charAt(sortedStr.length-1)) !== -1;

This checks for duplicates at the start, middle, or end of the sorted string representation of the array.

Example 2: Grab the middle value of a sorted array #

If you need the middle element of an array (assuming an odd length), you can use sort() to order it, then calculate the index using the length property—no conditionals required:

const numbers = [5, 2, 9, 1, 7];
const middleValue = numbers.sort((a, b) => a - b)[Math.floor(numbers.length / 2)];

The sort comparator ensures we order numerically instead of lexicographically, and Math.floor helps us get the exact middle index without loops or conditionals.

If you can share your exact code snippet so far and what you’re aiming to accomplish at that ? position, I can give you a tailor-made solution that sticks strictly to all your constraints!

内容的提问来源于stack exchange，提问作者Newbie