Function that takes string and returns string reversed

Question

What is wrong with the following code

function FirstReverse(str) { 
  var backwards = "";
  for(var i = str.length; i>=0;i--){
     backwards += str[i];
      }
  str = backwards;  
  return str; 

}

// keep this function call here 
// to see how to enter arguments in JavaScript scroll down
FirstReverse(readline(str));

this is the first challenge on http://coderbyte.com/CodingArea/GuestEditor.php?ct=First%20Reverse&lan=JavaScript the only error it returns is ReferenceError: readline is not defined, but readline is what the site says to use. What is wrong here?

score 1 · Answer 1 · edited May 23 '17 at 11:57

1

Try this:

function reverse(s){
    return s.split("").reverse().join("");
}

Caveats : https://stackoverflow.com/a/16776621/1636522.

edited May 23 '17 at 11:57

Community

1
1

answered Apr 17 '14 at 03:10

super

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thefourtheye · Answer 2 · 2014-04-17T03:18:09.487

1

The readline function doesn't take any arguments. Simply remove str and keep the line like this
```
FirstReverse(readline());
```
You are starting your loop with i = str.length, so when you do str[i] for the first time, you will get undefined. So, you should be starting from str.length - 1.
Also you can return the backwards directly, you don't have to store it in str back, before returning.

function FirstReverse(str) {
    var backwards = "";
    for (var i = str.length - 1; i >= 0; i--) {
        backwards += str[i];
    }
    return backwards;
}

Also, I tested with these changes and it works.

edited Apr 17 '14 at 03:18

answered Apr 17 '14 at 03:11

thefourtheye

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@OneKitten I tested it on their site. They do some preprocessing it seems. – thefourtheye Apr 17 '14 at 03:14
Ah, it's one of those coding example sites -- that would make sense. – Qantas 94 Heavy Apr 17 '14 at 03:15

score 0 · Answer 3 · answered Apr 17 '14 at 03:10

0

The first time the loop body is executed, i will have the value of str.length. That is one beyond the last element of the str, which is at index str.length - 1.

Fixed code:

function FirstReverse(str) { 
  var backwards = "";
  for (var i = str.length - 1; i >= 0; i--) {
     backwards += str[i];
  }
  str = backwards;  
  return str; 
}

answered Apr 17 '14 at 03:10

Timothy Shields

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i understand my error and this makes sense, but it still returns the same error, could it be a bug on the site itself? – Justin Apr 17 '14 at 03:13

score 0 · Answer 4 · answered Apr 17 '14 at 03:11

It should be

function FirstReverse(str) { 
  var backwards = "";
  for(var i = str.length - 1; i>=0;i--){
     backwards += str[i];
      }
  str = backwards;  
  return str; 

}

because when indexing it begins from 0 to the length minus one of the string

score 0 · Answer 5 · answered Apr 17 '14 at 03:12

0

Try

function FirstReverse(str) { 
  var backwards = "";
  for(var i = str.length - 1; i>=0; --i){
     backwards += str[i];
  }
  return backwards;  
}

answered Apr 17 '14 at 03:12

Ed Heal

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still got the same error, i think there is something wrong with the sites example – Justin Apr 17 '14 at 03:16

score 0 · Answer 6 · answered Dec 24 '20 at 09:59

You can apply this below code.

function FirstReverse(str) { 
  var backwards = "";
  for(var i = str.length - 1; i>=0; --i){
     backwards += str[i];
  }
  return backwards ;  


}
   
// keep this function call here 
console.log(FirstReverse(readline()));

It means when you write something on input, it will give you a reverse result.

Function that takes string and returns string reversed

6 Answers6