Array Question

Hey, im making a SpaceShooter game and I am using 2 arrays to hold enemys and lasers so that I can use for…in loops to detect collision and such. I have a function that spawns the enemy or laser and puts them into the array[aray.length], but when i have them destroyed I realized I can’t delete its spot in the array, which ends up slowing down my game after a while. Does anyone know how I can keep this array clean?