There are a number of products that plug into the USB port to cast light on the keyboard.
But that is not a life hack solution, it is product recomendation.
The life hack solution is to tip the screen forward
so the light from the screen lights the keyboard .
lifehacks.stackexchange.com/users/13/James Jenkins
Go to another room / area where you can turn on the light: kitchen, bathroom(?), balcony, porch...
This has a double advantage:
it helps you use your laptop;
the light from the laptop's screen will not bother your room-mates.
A higher tech alternative is to use a forehead lamp.
Some of them even have the ability to adjust the light intensity.
However, every time you will look around, you will "blind" your room-mates.
lifehacks.stackexchange.com/users/26845/virolino
I'm not sure if you're already able to, but an alternative solution is to learn touch typing .
This has the advantage of being faster as well.
(This answer has been typed without directly looking at the keyboard, but admittedly not in complete darkness.)
lifehacks.stackexchange.com/users/5345/Glorfindel
Not exactly a hack.
Search online for "luminous keyboard stickers".
Make sure however they use Light Charged Paints as described in this article that warns against old-fashioned radioactive paint.
https://www.vintagewatchstraps.com/luminous.php#:~:text=Radium%20based%20luminous%20paint%20was%20banned%20in%20the,health%20grounds%2C%20is%20plain%20wrong%20and%20highly%20irresponsible .
I claim no scientific or medical knowledge on this subject
so I suggest doing your own research before buying.
lifehacks.stackexchange.com/users/9368/chasly - reinstate Monica
There are a multitude of devices intended for illuminating a book or kindle, that are a battery and switch with a built in clamp, a flexible neck and a white LED.
One of these should fit your laptop lid
That's if you don't fancy buying, or making, an "led on one end of a flexible metal arm, and a USB plug on the other" In terms of stuff you already have, perhaps use some string to make a necklace, tuck it behind your phone in its protective case (or even just tie it like a gift wrap
so it holds your phone)
then sling your phone round your neck with the torch activated.
You could keep it plugged in to remain charged.
If you have a desk stand you could put your phone in that.
If you don't have a desk stand, you could make one (shape one out of modeling clay, cut a slot into a potato etc then wrap it in sarin wrap so it doesn't contaminate the phone) or repurpose a phone holder intended for a car (one that clips your phone to the AC vents)
so it holds your phone at the top of the screen, looking down onto the keys
lifehacks.stackexchange.com/users/25171/Caius Jard
After my friends go to sleep they turn off the light at night. So I can't see my keyboard of my old laptop that has no LED under those key. It slows down my coding practices and other works significantly.  Is there any good suggestion for this? TIA.  .  Edit: As @James Jenkins and some others suggested, there are several types of  USB Light  that might be very useful I think. Like this one:   Google it...
Can't see my laptop keyboard at night
lifehacks.stackexchange.com
<laptop>
lifehacks.stackexchange.com/questions/23776
lifehacks.stackexchange.com/users/31715/Shafin Iqbal
There are a few ways that you could better see your keyboard at night, but the most obvious solution is probably to go to another room or an area where you can turn on the light. Failing this as an option, you could purchase a USB light for your laptop or buy some luminous keyboard sitckers. The options are to get a light that plugs into the USB port, go to another room, learn to touch type or get a luminous sticker.
There are a few ways that you could better see your keyboard at night, but the most obvious solution is probably to go to another room or an area where you can turn on the light. Failing this as an option, you could purchase a USB light for your laptop or buy some luminous keyboard sitckers. You could use a forehead lamp or lamps designed for illuminating a book or kindle which clamp on. There are also luminous keyboard stickers available. Another solution is to merely tip your screen forward so it shines on the keyboard. Or you could learn touch typing.
A number of products are available that plug into the USB port to cast light on the keyboard.  Some people tip the screen forward to light the keyboard. Learning to touch type might be an option, or you could move to another room where you can turn on the light. There are a few different solutions for this. The simplest would be to go into another room where you can turn on the light. However, if this is not possible, you could tilt the screen or buy a USB-powered lamp to cast light on the keyboard. Another potential solution would be to learn to touch type so that you don't need to see the keyboard.
Get a light that plugs into the USB port. Go to another room. Learn to touch type. Get a luminous sticker.
You could use a forehead lamp or lamps designed for illuminating a book or kindle which clamp on. There are also luminous keyboard stickers available. Another solution is to merely tip your screen forward so it shines on the keyboard. Or you could learn touch typing.
You could cast light on the keyboard either by tilting the computer screen or buying a USB powered lamp. If you learn to touch type, you won't need to see the keyboard. You could also relocate to another room where you can turn on the light.