js function to calculate combinations of elements in Array

const values = [1,2,null,3].map((x) => !!x || null);
const vlength = values.length;
let combinations = [];
for (let i = 0; i < vlength; i++) {
    if (values[i]) {
        let acc = [];
        acc.push(new Array(vlength).fill(null).fill(true, i, i + 1));
        for (let j = vlength - 1; j > i; j--) {
            if (values[j]) {
                acc = acc.concat(
                        acc.map((x) => x.slice().fill(true, j, j + 1)));
            }
        }
        combinations = combinations.concat(acc);
    }
}