Flipping the order of characters is known as reversing of JavaScript string. The Internet has many questions about reverse algorithm. It is one of the common interview questions in technical interviews as well. A programmer is expected to know all the methods by which he/she can reverse a string.
There are multiple ways to reverse a string in popular programming languages. As JavaScript does not have a built-in reverse function, a coder can use other methods to reverse a string in JavaScript.
This tutorial will be explaining the answers to reverse a string with the help of three different techniques. The tutorial contains reverse code examples and their outputs to make the steps as simple as possible for string reversal.
Table of Contents
Approach#01: The Quick Way by using JavaScript Built-In Methods.
In this reverse technique, three methods will be used.
- The split( ) method splits the String object to separate the strings as sub-strings into an array.
- The reverse( ) method does the main job and reverses the array. It makes the first element of an array the last, and the last one becomes the first.
The join( ) method is used to rejoin the previously separated and reversed string as the final step.
Example Code
function reverseString(str) {
// Step 1. Use the split() method to return a new array
var splitString = str.split("");
// Step 2. Use the reverse() method to reverse the new created array
var reverseArray = splitString.reverse();
// Step 3. Use the join() method to join all elements of the array into a string
var joinArray = reverseArray.join("");
//Step 4. Return the reversed string
return joinArray;
}
reverseString("WELCOME");
Output:
Three Methods can be Chained Together
Example Code
function reverseString(str) {
return str.split("").reverse().join("");
}
reverseString("JAVA"); Output
These functions can be used in this approach only if it is allowed to use the JS built-in methods; otherwise, there are few more techniques.
Approach#02: The Old Way using For Loop.
In this technique, code with a traditional loop is used instead of the built-in functions of JavaScript. Loop iteration is used to reverse a string.
Example Code
function reverseString(str) {
// Step 1. Create an empty string that will get the new created string
var newString = " ";
// Step 2. Create the FOR loop
for (var i = str.length - 1; i >= 0; i--) {
newString += str[i];
}
// Step 3. Return the reversed string
return newString; // "olleh"
}
reverseString('Software');
Output
Approach#03: Reversing using Recursion.
The last method that is used to solve this problem is the recursive approach. This technique has two methods:
substr( ): This method will extract a string part that is beginning at some character on the specified location, and return specified number of characters.
"table".substr(1); // "able" charAt( ): This method is used to get the specified index character from a string.
"table".charAt(0); // "t" Example Code
function reverseString(str) {
if (str === "")
return "";
else
return reverseString(str.substr(1)) + str.charAt(0);
}
reverseString("BINARY");
Output
This approach is not efficient, and it is quite slow in the cases where we have a long string as the length of string decides the depth of Recursion.
Conclusion
The Reversing of String in JavaScript is a simple problem, but it requires the perfect solution as per the demands of an interviewer or your own choice in programming. The above-explained solutions vary from simple to complex solutions, and it depends on the programmer to choose the best one according to his/her needs.
We hope you found this tutorial easy and helpful!
