How do you reverse a string in place in JavaScript?

Question

How do you reverse a string in place (or in-place) in JavaScript when it is passed to a function with a return statement, without using built-in functions (.reverse()<

Answer 1

Best ways to reverse a string in JavaScript

1) Array.reverse:

You’re probably thinking, wait I thought we were reversing a string, why are you using the Array.reverse method. Using the String.split method we are converting our string into an Array of characters. Then we are reversing the order of each value in the array and then finally we convert the Array back to a String using the Array.join method.

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

2) Decrementing while-loop:

Although pretty verbose, this solution does have its advantages over solution one. You’re not creating an array and you’re just concatenating a string based on characters from the source string.

From a performance perspective, this one would probably yield the best results (although untested). For extremely long strings, the performance gains might drop out the window though.

function reverseString(str) {
    var temp = '';
    var i = str.length;

    while (i > 0) {
        temp += str.substring(i - 1, i);
        i--;
    }


    return temp;
}
reverseString('dwayne');

3) Recursion

I love how simple and clear this solution is. You can clearly see that the String.charAt and String.substr methods are being used to pass through a different value by calling itself each time until the string is empty of which the ternary would just return an empty string instead of using recursion to call itself. This would probably yield the second best performance after the second solution.

function reverseString(str) {
    return (str === '') ? '' : reverseString(str.substr(1)) + str.charAt(0);
}
reverseString('dwayne');