Basic Algorithm Scripting - Reverse a String

JavaScript
1

Tell us what’s happening:
Describe your issue in detail here.
So i was tasked to reverse a string and this is my code. When i run it it return “undefinedello” which doesnt make any sense. Can someone please tell me whats is wrong with it?
Your code so far

let newStr = "";
function reverseString(str) {
  for (let i = 0; i < str.length; i++) {
    const s = str.length - i;
    newStr += str[s];
  }
  return newStr
}

console.log(reverseString("hello"));

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Challenge: Basic Algorithm Scripting - Reverse a String

Link to the challenge:

2 
const s = str.length - i;
newStr += str[s];

If the string is 5 characters long, then the first time through the loop i will be 0. So what is s going to equal? And what is the last index number for a string that is 5 characters long?

This should be defined inside the function body. Do not use global variables.

3

The issue in your code is with the index calculation inside the loop.
JavaScript uses zero-based indexing, so the last character of a string with length n is at index n - 1 .

In your code, you’re using str.length - i as the index, but it should be str.length - 1 - i because JavaScript utilizes zero-based indexing, where the first character in a string has an index of 0, and the last character has an index of str.length - 1 . In your code, you’re using str.length - i as the index, but this is incorrect because it skips the last character during iteration. The correct approach is to use str.length - 1 - i as the index.

let newStr = "";
function reverseString(str) {
  for (let i = 0; i < str.length; i++) {
    const s = str.length - 1 - i;
    newStr += str[s];
  }
  return newStr
}

console.log(reverseString("hello"));

Futher you can consider this detailed blog as well.

4

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