Night Markets (pasar malam, in Malay language, is popular called here) especially the big ones are worth your effort to visit to. You can find varieties of edible food and non edible goods in night markets. The prices are reasonable cheap as compared to the shops. There are plenty of delicious local street food you can find in the night markets. Try them out yourself, you will appreciate the delicious street food there. As the goods are cheap in night markets so please do not expect a 100% good in quality, but with the price it's worth buying the items that suit you.
You can find edible food such as fried noodle,
You can bargain for the goods but it's unlikely that you will get a big discount. Some stall owners may give you a small discount while some may not offer any discount.