Get product result of the given arrays (JavaScript)

combination.js

const a = [ 1, 2, 3, 4 ];
const b = [ 5, 6, 7 ];
const c = [ 8, 9 ];

const d = { a, b, c }

function combinations(aryOfAry) {
  const combination = (a1, a2) => {
    let a = []
    a1.forEach((v1) => {
      a2.forEach((v2) => {
        let t = v1.slice();
        t.push(v2);
        a.push(t);
      });
    });
    return a;
  }

  let base = [[]];
  aryOfAry.forEach((v) => {
    base = combination(base, v);
  });
  return base;
}

console.log(combinations(Object.values(d)));