How to reverse the order in a FOR loop

Question

I\'ve a simple FOR statement like this:

var num = 10,
    reverse = false;

for(i=0;i

when rever

Answer 1

I just came across the need for this the other day. Here's how I did it:

var num = 10,
    i = 0,
    direction = 1, 
    reverse = false;

if(reverse)
    i = num + (direction = num = -1);

for(; i !== num; i += direction) {
    console.log(i);
}

No need for separate loops, and no need to do math to calculate the proper i in the loop.

So if reverse is true...

• i (which represents our first item) becomes num - 1, so we're now starting on what would have been the last item

• num (which represents out of bounds) becomes -1, so we're now stopping on what would have been the first item

• direction is -1, which means it will decrement when we do i += direction

So by swapping our starting point with our ending point and changing the alteration of i from 1 to -1, we'll be going up or down based on those modifications.