Multiplica todos los valores de un array de arrays

mutiplyAll()

const mutiplyAll=arr=>{let r=[];arr.forEach(x=>{x.forEach(y=>{return r.push(y)})});return r.reduce((acc, n) => n * acc)};
console.log(mutiplyAll([[1,2], [3,4], [5,6,7]])); //5040