sumConsecutiveOnes.js

const arr = [1,1,0,0,1,1,1,0,1];

function sumConsecutiveOnes(arr) {
    return [...arr, 0].reduce((acc, value) => {
        if(value === 1) {
            acc.counter += 1;
        } else if(acc.counter > 0) {
            acc.output.push(acc.counter);
            acc.counter = 0;
        }
        return acc;
    }, {
        output: [],
        counter: 0,
    }).output;
}

console.log(sumConsecutiveOnes(arr));