JavaScript数组排序结果不符及去重需求技术问询

Hey there! Let's tackle your problem step by step—you've got two main things to fix here: getting the numeric sort right, and removing those duplicate values.

1. Why the default sort() isn't working as expected #

The default sort() method in JavaScript sorts elements as strings, not numbers. That's why you're seeing [1, 21, 30, 4]—it's comparing the string representations of the numbers, so "4" comes after "30" because "4" has a higher Unicode value than "3".

To fix numeric sorting, you need to pass a comparator function to sort():

array1.sort((a, b) => a - b);

This tells JavaScript to compare the values numerically: if a - b is negative, a comes before b (ascending order).

2. Removing duplicate values #

There are a few clean ways to do this, but one of the simplest is using a Set—a JavaScript object that only stores unique values. You can convert your sorted array to a Set, then convert it back to an array.

Putting it all together #

Here's the full code that does both sorting and deduplication:

var array1 = [1, 1, 30, 4, 21];
// First sort numerically
array1.sort((a, b) => a - b);
// Then remove duplicates using Set
var uniqueSortedArray = [...new Set(array1)];
console.log(uniqueSortedArray); // Output: [1, 4, 21, 30]

Alternative: Deduplicate without Set (for older environments) #

If you need to support environments that don't have Set, you can loop through the sorted array and only keep unique values:

var array1 = [1, 1, 30, 4, 21];
array1.sort((a, b) => a - b);
var uniqueSortedArray = [];
for (let i = 0; i < array1.length; i++) {
  if (array1[i] !== array1[i - 1]) {
    uniqueSortedArray.push(array1[i]);
  }
}
console.log(uniqueSortedArray); // Same output: [1, 4, 21, 30]

That should give you exactly the result you're looking for!

内容的提问来源于stack exchange，提问作者Mitesh