let arr = [ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], ] let value = [] arr.forEach((item) => { item.forEach((val) => { value.push(val) }) }) console.log(value);