let inputString = 'AABBCCCCBDDDADB';



function candyCrunch(str) {
    for(let i = 0; i < str.length; i++) {
        let counter = 0;
        if( i > (str.length - 3)) {
            return str;
        }
        while(str.length[j = i] === str.length[++j]) {
            counter++;
        }

        if(counter >= 3) {
            str.splice(i, counter);
        }
    }
    return str;
}


let temp = candyCrunch(inputString);

console.log(temp);