Алгоритм сжатия RLE

RLE.js

function getRLEStringLength(str) {
    if(!str)
        return 0;

    let length = 0,
        tempCount = 0,
        symbol = str[0];
    
    for(let i = 0; i < str.length; i++) {
        if(symbol == str[i]) {
            tempCount++;
        }

        if(symbol != str[i] || i === str.length - 1) {
            length += tempCount.toString().length + 1;
            symbol = str[i];
            tempCount = 0
        }
    }

    return length;
}

function getRLEString(str) {
    length = str != null ? str.length : 0;
    compressStrLength = getRLEStringLength(str);
    if (length == 1 || compressStrLength >= str.length) {
        return str;
    }

    let tempCount = 0,
        symbol = str[0],
        compressStr = "";
    
    for(let i = 0; i < str.length; i++) {
        if(symbol == str[i]) {
            tempCount++;
        }

        if(symbol != str[i] || i === str.length - 1) {
            compressStr += symbol.toString() + tempCount;
            symbol = str[i];
            tempCount = 1
        }
    }

    return compressStr.toString();
}