const flat = arr => [].concat.apply([], arr.map(a => Array.isArray(a) ? flat(a) : a));
// Or
const flat = arr => arr.reduce((a, b) => Array.isArray(b) ? [...a, ...flat(b)] : [...a, b], []);

// Or
// See the browser compatibility at https://caniuse.com/#feat=array-flat
const flat = arr => arr.flat();

// Example
flat(['cat', ['lion', 'tiger']]);   // ['cat', 'lion', 'tiger']

<div className="md:self-start sticky top-16 bg-background px-4 mt-1 sm:px-6 md:pt-4 lg:pl-8 lg:pr-4">
          <ScrollArea className="whitespace-nowrap">
            <div className="w-max flex md:flex-col gap-1 bg-transparent text-muted-foreground pb-2">
              {menuData.map((section) => (
                <Button
                  key={section.title}
                  onClick={() => handleScrollToSection(section.title)}
                  variant="ghost"
                  size="sm"
                  className={cn(
                    'w-auto md:w-full hover:cursor-pointer relative md:justify-end',
                    activeSection === section.title
                      ? cn(
                          'text-foreground after:absolute after:bottom-[-2px] after:bottom-0 after:w-full after:h-[2px] after:bg-primary',
                          'md:after:right-[-2px] md:after:top-0 md:after:h-full md:after:w-[2px]',
                        )
                      : '',
                  )}
                >
                  {section.title}
                </Button>
              ))}
            </div>
            <ScrollBar orientation="horizontal" />
          </ScrollArea>
        </div>

const gcd = (...arr) => {
  const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
  return [...arr].reduce((a, b) => _gcd(a, b));
};

gcd(8, 36); // 4
gcd(...[12, 8, 32]); // 4

console.log("xa")

class SequentialQueue{	//if you want it to go backwards, too bad
	next(){
		return this.i++;
	}
	constructor(start = 0){
		this.i = start;
	}
}
const que = new SequentialQueue(0);
for(let i = 0; i < 10; i++){
	console.log(que.next());
}

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function(nums) {
    return new Set(nums).size !== nums.length
};