How to reverse the order in a FOR loop

user_257808 0
Viewed 48612

I've a simple FOR statement like this:

var num = 10,
    reverse = false;

for(i=0;i<num;i++){
    console.log(i);
}

when reverse is false I want it to return something like [0,1,2,3,4,5,6,7,8,9]

but, when reverse is true, it should return [9,8,7,6,5,4,3,2,1,0]

Which is the most efficient way to get this result, without checking every time if reverse is true or false inside the loop?

I don't want to do this:

var num = 10,
    reverse = false;

for(i=0;i<num;i++){
    if(reverse) console.log(num-i)
    else console.log(i)
}

I would like to check reverse only one time outside the loop.

for-loop javascript performance
12 Answers
//reverse a number
let c = [2,3,5,67,4]
let sum = '';
let d = c.toString().split('')
console.log(d)
for(let i = d.length-1; i >= 0; i--) {
    sum += d[i]
}
console.log(sum)
user_124156750
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