Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

To solve this problem in JavaScript, you can use a similar approach as you would in Python. You can use a Set to keep track of the elements you've seen. If you encounter an element that's already in the set, it means there's a duplicate, and you can return true. If you go through the entire array without finding a duplicate, you return false. Here's a JavaScript function that implements this logic:

function containsDuplicate(nums) { let seen = new Set(); for (let num of nums) { if (seen.has(num)) { return true; } seen.add(num); } return false; }

You can use this function containsDuplicate by passing an array of integers, and it will return true if there's any duplicate or false if all elements are distinct.