Example 1: Reverse a String Using for Loop
// program to reverse a string
function reverseString(str) {
// empty string
let newString = "";
for (let i = str.length - 1; i >= 0; i--) {
newString += str[i];
}
return newString;
}
// take input from the user
const string = prompt('Enter a string: ');
const result = reverseString(string);
console.log(result);
Output
Enter a string: hello world dlrow olleh
In the above program, the user is prompted to enter a string. That string is passed to the reverseString()
function.
Inside the reverseString()
function,
- An empty newString variable is created.
- The
for
loop is used to iterate over the strings. During the first iteration,str.length - 1
gives the position of the last element. That element is added to the newString variable.
This process continues for all the string elements. - The value of i decreases in each iteration and continues until it becomes 0.
Example 2: Reverse a String Using built-in Methods
// program to reverse a string
function reverseString(str) {
// return a new array of strings
const arrayStrings = str.split("");
// reverse the new created array elements
const reverseArray = arrayStrings.reverse();
// join all elements of the array into a string
const joinArray = reverseArray.join("");
// return the reversed string
return joinArray;
}
// take input from the user
const string = prompt('Enter a string: ');
const result = reverseString(string);
console.log(result);
Output
Enter a string: hello olleh
In the above program, the built-in methods are used to reverse a string.
- First, the string is split into individual array elements using the
split()
method.str.split("")
gives ["h", "e", "l", "l", "o"]. - The string elements are reversed using the
reverse()
method.arrayStrings.reverse()
gives ["o", "l", "l", "e", "h"]. - The reversed string elements are joined into a single string using the
join()
method.reverseArray.join("")
gives olleh.