Recursive string reversal function in javascript?

Recursive string reversal function in javascript?

I'm a pretty experienced frontend engineer with a weak CS background. I'm trying to get my head around the concept of recursion. Most of the examples and purported explanations I can find just aren't explaining it in a way I find easy to understand.

I set myself a task of writing a function that will reverse a string recursively. I know there has to be a base condition (i.e. the solution is found), but I can't figure out how to actually write something like this and could use a demo to study.

Could someone provide a sample function?

Answer by Development 4.0 for Recursive string reversal function in javascript?

This is a pretty straightforward C# implementation of the algorithm you asked for. I think it could be rewritten in javascript pretty easily.

/*  C#: The Complete Reference   by Herbert Schildt     Publisher: Osborne/McGraw-Hill (March 8, 2002)  ISBN: 0072134852  */      // Display a string in reverse by using recursion.     using System;     class RevStr {       // Display a string backwards.     public void displayRev(string str) {       if(str.Length > 0)          displayRev(str.Substring(1, str.Length-1));       else          return;         Console.Write(str[0]);     }   }     public class RevStrDemo {     public static void Main() {         string s = "this is a test";       RevStr rsOb = new RevStr();         Console.WriteLine("Original string: " + s);         Console.Write("Reversed string: ");       rsOb.displayRev(s);         Console.WriteLine();     }   }  

Answer by Tom for Recursive string reversal function in javascript?

Something like:

function reverse (str) {      if (str === "") {          return "";      } else {          return reverse(str.substr(1)) + str.charAt(0);      }  }  

So the function is recursive as it calls itself to do the work.

Answer by Gerrat for Recursive string reversal function in javascript?

Try this(untested):

def resurse(s) {      if (s.length == 0) {        return '' // stopping condition      } else {  // return last char + result of function called with chars up to last char        return s.substring(s.length, s.length -1) + recurse(s.substring(1, s.length -1))    }    

Answer by maerics for Recursive string reversal function in javascript?

A tail recursive version, just for kicks (even though JavaScript doesn't perform tail call elimination):

function reverse(str) {    function r(s, acc) {      return (s.length == 0) ? acc : r(s.substr(1), s.charAt(0) + acc);    };    return r(str, '');  };  

Answer by Jonathan Borthwick for Recursive string reversal function in javascript?

It is verbose, but I like making it easy to understand in logical steps:

function rev(soFar, count){     console.log("asString: " + soFar );     console.log("count: " + count);     var len = soFar.length;     var ret = soFar;//ret needs to be a reference to soFar     if(len > count){        var subd = soFar.substring(1,len);        var first = soFar[0];        //we want to inject the first letter at the index position one back from the length, minus what the count is at this point        var indexOfInsert = len-1 - count;//so if count is 0 and length is 5, we want 4 (4 -0)        var asArray = subd.split("");        asArray.splice(indexOfInsert,0,first);        count++;//need to increment count for the next round        var asString = "";      //recreate as string, not array - the default toString() makes this a comma delimited string. It is best toi just recreate it in a loop      for(var i = 0; i

}

Then call it like:

var reversed = rev("Hello",0);  console.log("result",reversed);  

Answer by qweszxcj for Recursive string reversal function in javascript?

So far the best I think:

function reverse(s) {      if (s.length===1) return s;      return reverse(s.slice(1)) + s[0];  }  

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