How to Reverse a String In-Place in JavaScript?

In-Place String Reversal in JavaScript

When working with strings in JavaScript, there may be situations where you need to reverse a string in-place without relying on built-in functions like .reverse() or .charAt(). This can be achieved when the string is passed to a function with a return statement.

To reverse a string in-place:

• Convert to Array: Use the split('') function to convert the string into an array of characters.
• Reverse Array: Utilize the reverse() method on the resulting array to reverse the order of characters.
• Join Array: Finally, use the join('') function to concatenate the reversed characters back into a string.

Example 1 (ASCII Characters):

function reverse(s) {
    return s.split("").reverse().join("");
}

const original = "Hello";
const reversed = reverse(original);
console.log(reversed); // "olleH"

Example 2 (Unicode Support):

For strings containing multi-byte characters (e.g., UTF-16), a Unicode-aware solution is necessary.

• Use Array Expansion Operator: The ... operator (spread operator) creates a new array with individual characters. This supports Unicode characters and yields valid unicode strings.

function reverse(s) {
    return [...s].reverse().join("");
}

• Split with Unicode Flag: Alternatively, you can use split() with the u (Unicode) flag as a separator, which also supports Unicode characters.

function reverse(s) {
    return s.split(/(?:)/u).reverse().join("");
}

By implementing these solutions, you can effectively reverse a string in-place within a function, regardless of the character set used.

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