arr3 = [...Array(3).keys()];
arr4 = [...Array(3).keys()];
arr3.forEach((element) => {
arr4.forEach((element1) => {
console.log(element1);
});
});
arr3 = [...Array(3).keys()];
arr4 = [...Array(3).keys()];
arr9 = [...arr3, ...arr4];
arr9.forEach((element) => {
console.log(element);
});