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Code Golf · #41 · 2026-05-15

Run-length encode

Difficulty 3/3 · JavaScript

How to play

Write a JavaScript function body that passes all test cases using the fewest characters. Run against examples first, then submit for the full test suite. Eagle < Birdie < Par.

Given a string, run-length encode it: consecutive identical characters become the character followed by its count. e.g. "aaabbc" → "a3b2c1".

Examples

f("aaabbc") a3b2c1
f("abc") a1b1c1

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Your code (function body — receives input)

function(input) { 0 chars
}

Write the shortest JavaScript function body that passes all tests · Back to hub