How to keep selected option values when submitting form

Question

I want to submit an html form and to keep some drop down lists selected how can I do that please help me.

Answer 1

you can set the index value as 0,1,2....
if index value is set -1 then it will not select any option in drop down but once you set index value >-1 form will shows the selected value in drip down once page is loaded