Increment Query

I have a technical question here regarding the limits of incrementation. I’d like to increment a value by the amount of its value. For example, if i = 25, then I don’t want to increment like so (++i = 26); rather, I would like to increment it like (++i=50). Now, I realize that the ++ does not do this, but I was wondering if there was an operation that I’m not aware of that will do this. I’m not expecting there to be, but I couldn’t find any evidence of this and just wondered if I wasn’t searching for the appropriate term.
My feeling is that this needs to be a function that applies this formula to a valye with each iteration, but I was wondering if there was an operation I was unaware of that would also handle something like this.

The operator you’re looking for is +=. Namely foo += amount

So after let i = 5; i += 10, the value of i will be 15.

If you want to add the value of an item to itself, you’re really multiplying it by 2. In which case you can do i *= 2