JavaScript reverses a string in place refers to the process of flipping the order of characters within the string without using additional memory. It involves iterating through the string and swapping characters from both ends until reaching the middle.
Reverse a string in place Example
Using the JavaScript split() method
JavaScript String split() Method is used to split the given string into an array of strings by separating it into substrings using a specified separator provided in the argument.
Example: This example reverses the string by first splitting it with (“”) separator and then reversing it and finally joining it with (“”) separator.
let str = "This is GeeksForGeeks" ;
console.log( "Input string is : " + str);
function gfg_Run() {
console.log(
"Reverse String" +
str.split( "" ).reverse().join( "" )
);
} gfg_Run(); |
Input string is : This is GeeksForGeeks Reverse StringskeeGroFskeeG si sihT
Using the Array reverse() method
JavaScript Array.reverse() Method is used for the in-place reversal of the array. The first element of the array becomes the last element and vice versa.
Example: This example uses the concept of the merge sort algorithm.
// Input sting let str = "This is GeeksForGeeks" ;
console.log( "Input string is : " + str);
// Function to reverse string function reverse(s) {
if (s.length < 2) return s;
let hIndex = Math.ceil(s.length / 2);
return (
reverse(s.substr(hIndex)) +
reverse(s.substr(0, hIndex))
);
} // Function to display output function gfg_Run() {
console.log(reverse(str));
} // Function call gfg_Run(); |
Input string is : This is GeeksForGeeks skeeGroFskeeG si sihT
Using the Array join() method
The JavaScript Array join() Method is used to join the elements of an array into a string. The elements of the string will be separated by a specified separator and its default value is a comma(, ).
Example: This example takes a variable and appends the result from the end of the string.
// Input sting let str = "A Computer Science Portal" ;
console.log( "Input string is : " + str);
// Function to reverse string function reverse(s) {
// Variable to store reverse
let o = "" ;
for (let i = s.length - 1; i >= 0; o += s[i--]) {}
return o;
} // Function to display output function gfg_Run() {
console.log(reverse(str));
} // Function call gfg_Run(); |
Input string is : A Computer Science Portal latroP ecneicS retupmoC A
Using substr() method
JavaScript str.substr() method returns the specified number of characters from the specified index from the given string. It basically extracts a part of the original string.
Example: This example uses str.substr() method to reverse a string.
// Input sting let str = "This is GeeksForGeeks" ;
console.log( "Input string is : " + str);
// Function to reverse string function reverse(s) {
if (s.length < 2) return s;
let hIndex = Math.ceil(s.length / 2);
return (
reverse(s.substr(hIndex)) +
reverse(s.substr(0, hIndex))
);
} // Function to display output function gfg_Run() {
console.log(reverse(str));
} // Function call gfg_Run(); |
Input string is : This is GeeksForGeeks skeeGroFskeeG si sihT
Using for loop
To reverse a string in place using a for loop in JavaScript, iterate over half the string length, swapping characters from both ends until reaching the middle. Return the modified string.
Example: In this example the function iterates backward through the string, appending each character to a new string, effectively reversing it. Then, it returns the reversed string.
// reverse string using for loop function reverseString(str) {
let reversed = '' ;
for (let i = str.length - 1; i >= 0; i--) {
reversed += str[i];
}
return reversed;
} let str = 'This is GeekForGeeks' ;
console.log( "Original string is: " ,str);
console.log( "Reversed string is: " ,reverseString(str));
|
Original string is: This is GeekForGeeks Reversed string is: skeeGroFkeeG si sihT