aria.js

let input = "aabbccdaaaabb";
let output = [];

for (let i = 0; i < input.length; i++) {

    let current = input[i];
    let charStream = current.toString();
    let offset = 0;

    if (input[i - 1] != input[i] && input[i + 1] != input[i]) {
        output.push(charStream);
        continue;
    }

    if (input[i - 1] == input[i]) continue;

    for (let j = i + 1; j < input.length; j++) {
        if (input[j] == current) {
            offset++;
            charStream += input[j].toString();
        } else {
            i += offset;
            break;
        };
    }
    output.push(charStream);
}

console.log(output)