Run length encoding is a simple way to compress a string of characters by replacing repeated characters with a single character and the number of times it appears in the original string.
For example, the string "AAABBCCCD" can be compressed to "A3B2C3D1". In this example, the letter "A" appears three times in a row, so it is replaced with "A3". The letter "B" appears twice in a row, so it is replaced with "B2". The letter "C" also appears three times in a row, so it is replaced with "C3", and the letter "D" appears once, so it is replaced with "D1".
To implement run length encoding in JavaScript, you can use the following code:
function runLengthEncode(str) {
// Initialize variables
let currentChar = str[0];
let currentCount = 1;
let result = "";
// Iterate through the string character by character
for (let i = 1; i < str.length; i++) {
// If the current character is the same as the previous character
if (str[i] === currentChar) {
// Increment the current count
currentCount++;
} else {
// If the current character is different from the previous character
// Append the current character and its count to the result
result += currentChar + currentCount;
// Set the current character and count to the new character and 1
currentChar = str[i];
currentCount = 1;
}
}
// After the entire string has been processed, append the current character and its count to the result
result += currentChar + currentCount;
// Return the compressed string
return result;
}
To use this function, you can simply call it with a string as the argument, like this:
let compressedString = runLengthEncode("AAABBCCCD"); // compressedString = "A3B2C3D1"
Run length encoding can only provide a significant compression for strings that contain many repeated characters. For strings with few or no repeated characters, the compressed string will actually be longer than the original string.