Find the starting and ending indices of all repeated characters from a string

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const input =“hellooooloo”;
const op = getRepeated(input);
console.log(op) // [(2,3), (4,7), (9,10)]

function Indicies(str){
    let res = [];
    let start = 0;
    let end = 1;

    while(start<=end && end<str.length){
        if(str[start]===str[end]){
            let diff =  end - start;
            if(diff==1 && end === str.length-1){
                res.push([start,end]);
            }
            end++;
        }else{
            let diff =  end - start;
            if(diff>1){
                res.push([start,end-1]);
            }
            start = end;
            end++;
        }
    }
    return res;
}
console.log(Indicies(input));