Q:

How to reverse a string using only one variable

How to reverse string using next conditions:
1) if string isn't parameter of function,
2) if string is place in global scope,
3) use loop like for, while,
4) can add one variable
Note: Can't use method .join, .split, .reverse and so on...
If it possible and not so hard for you make explain your solution, very grateful !

In other words, this is what you got:
 let s = 'any string';
 let p; // feel free to use at your discretion

 // your code here. No further variables, no functions and no built-ins
 // should console.log the reversed string

I'm understand that my solution is very close to my desire (conditions), but i can't generate other solution.

function convers(s){ //parameter 
 var str = "";//empty string for new converted string
 for(var i = s.length-1; i >= 0; i--)//loop decremebtation that count from end of string
 str+=s[i];//store result and assignments to str
 return str;// declare result 
}
console.log(convers("abcdef"));

I looked this source:
 javascript reverse string algorithm
Is there a faster Reverse String Algorithm for JavaScript? - but it is useless for me, sorry.
I'm sorry if my explanation is not clear enough. Sorry for my English, I'm beginner here :))))

A:

You could use a new variable for the reverted string and use the length property for iterating.

var string = 'abcdef',
    reverse = '';

while (reverse.length !== string.length) {
    reverse += string[string.length - 1 - reverse.length];
}
string = reverse;

console.log(string);

A bit shorter.

var string = 'abcdef',
    reverse = '';

while (reverse.length !== string.length) {
    reverse = string[reverse.length] + reverse;
}
string = reverse;

console.log(string);

