To conform to normally recognized standards you should use the code as you have written ie.
for(let i = 0; i < bobsFollowers.length; i++)
You could use:
let i, j; for(i=0; i < bobsFollowers.length; i++)
But it’s kinda unconventional. In the end, it’s your code, and you can do what you prefer. As long as you’re consistent, you and others will be able to decipher your code. If you’re looking to get hired as a developer, you’ll probably be required to follow established standards, so in my opinion, I would conform. Hope this helps!