How to reverse a string using only one variable in JavaScript

In this problem statement, our target is to print the reverse string using only one variable and implement the solution with the help of JavaScript. We can solve this problem with the help of loops in JavaScript.

Understanding the Problem

The given problem is stating that we have a string which we need to reverse using only one variable. In simple terms, if we have the string "Hello World", the reverse of this string will be "dlroW olleH".

Logic for the Given Problem

In order to reverse the given string with only one variable, we will start by creating an empty string variable. Then we will iterate using a for loop from the last character to the first character. In this phase we will append the current character to the reversed variable. After traversing all the characters, the reversed string will be achieved.

Algorithm

Step 1: Declare a variable for storing the reverse string and initialize it as empty.

Step 2: Iterate through the characters of the string using a for loop, starting from the last character.

Step 3: Inside the loop, append each traversed character to the variable created in step 1.

Step 4: Return the reversed string as the final output.

Example

// Function to get the reversed string
function reverseStr(str) {
   var reversed = '';
   
   // Iterate the string with a loop from last to first
   for (var i = str.length - 1; i >= 0; i--) {
      reversed += str[i];
   }
   
   return reversed;
}

var actualString = 'Hello, Tutorials Point!';
var reversedStr = reverseStr(actualString);
console.log("Original String:", actualString);
console.log("Reversed String:", reversedStr);

Original String: Hello, Tutorials Point!
Reversed String: !tnioP slairotuT ,olleH

Alternative Approach Using Built-in Methods

JavaScript provides built-in methods that can achieve the same result more concisely:

function reverseStrBuiltIn(str) {
   var reversed = str.split('').reverse().join('');
   return reversed;
}

var testString = 'JavaScript';
var result = reverseStrBuiltIn(testString);
console.log("Original:", testString);
console.log("Reversed:", result);

Original: JavaScript
Reversed: tpircSavaJ

Comparison

Complexity Analysis

Time Complexity: O(n), where n is the length of the string, because we need to iterate through each character once.

Space Complexity: O(n) for storing the reversed string, which has the same length as the input string.

Conclusion

We successfully demonstrated how to reverse a string using only one variable in JavaScript. The for loop approach provides good control over the process, while built-in methods offer more concise code for the same result.