How to reverse a string in JavaScript using a "for...in" loop?

Question

I have a piece of JavaScript code using a for loop to reverse a string. However, I would like to know if it is possible to use a for in loop instead and how would I go about that?

     function reverse(str){
         var reversedString = '';
         for (var i = str.length - 1; i >= 0; i--){
            reversedString = reversedString + str[i];
     }
     return reversedString;
   }

   alert(reverse('hello'));

Answer 1

From MDN Docs

for...in should not be used to iterate over an Array where the index order is important.

Array indexes are just enumerable properties with integer names and are otherwise identical to general Object properties. There is no guarantee that for...in will return the indexes in any particular order. The for...in loop statement will return all enumerable properties, including those with non–integer names and those that are inherited.

Because the order of iteration is implementation-dependent, iterating over an array may not visit elements in a consistent order. Therefore it is better to use a for loop with a numeric index (or Array.prototype.forEach() or the for...of loop) when iterating over arrays where the order of access is important.

let iterable = '1234567';
String.prototype.hello = "hello";  // doesn't affect
let reversed = "";
for (let value of iterable) {
  reversed = value + reversed;
}

console.log(reversed);