In this quick tutorial, we’re going to see how we can reverse a String in JavaScript .

We’ll start to do this processing using plain JavaScript first . Reverse a String is one of the most frequently asked JavaScript interview questions .

Furthermore, we’ll demonstrate how to reverse the order of words in a sentence. There are varierty of wasy to do this in javascript .Lets have a look at all the different ways .

Using JavaScript Built In Functions

One of the easiest way is to using a split function and then using the reverse() built in function and then concatening using join() method as below.

It is usually noob way if asked in interview . So avoid answering this in a interview.

function reverseString(input) {
  return input.split('').reverse().join('');
}

Reverse a String In JavaScript Using Loop

Have a look at the most basic way of doing this by iterating the string in reverse order and then returning it .

function reverse(input) {
  var ouPut = [];
  //consider input ='TEST'
  for (var i = input.length - 1, j = 0; i >= 0; i--, j++)
 
  
 ouPut [j] = input[i];
    
    
  return ouPut .join('');
}

Now with the given code where input="TEST" . Have a look at how the code executes

Iteration Number	i	j	input[i]	outPut[j]	Result outPut[]
First	3	0	T	T	[T]
Second	2	1	S	S	[T,S]
Third	1	2	E	E	[T,S,E]
Fourth	0	3	T	T	[T,S,E,T]

output.join(”) is the last line which joins the array and converts it as an String. Have a look at mozilla doc here on Array.join() .

Using Recursion to Reverse a String

We are going to use recursion to split first item using substr() method and then add it to the end of the string.

function reverse(inpStr){
 if(inpStr === ""){
  return inpStr
 }else{
  return reverse(inpStr.substr(1)) + inpStr[0] }
}