Strings & Text

JavaScript Program to Reverse a String

Learn modern and traditional techniques to reverse a string in JavaScript, including split-reverse-join, recursion, and for...of loops.

JavaScript Source Code

Editable code sample with line numbers

JavaScript

Expected Output

When this program is compiled and executed, the terminal outputs:

Original:  ZenCompiler Cloud IDE
Builtin:   EDI duolC relipmoCneZ
Loop:      EDI duolC relipmoCneZ
Unicode:   EDI duolC relipmoCneZ

How the Code Works

JavaScript strings are primitive and immutable. 1. The built-in method converts the string to an array of characters with split(''), reverses the array in place with reverse(), and joins the elements back into a string with join(''). 2. The decrementing loop iterates from the last index down to 0, appending each character to a new string. 3. The spread operator [...str] handles multi-byte Unicode surrogate pairs correctly.

Time Complexity

O(N)

Space Complexity

O(N)

Key Takeaways & Best Practices

Strings cannot be modified in place in JavaScript.
Use the spread operator [...str] when dealing with emojis or complex Unicode code points.

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