How i make drop down field and input field on same field.
Please be more specific about what you want. Else noone will be able to help you with your problem. 
i have a dropdown field in html file from where i can select the dropdown value to select but i also want if value is not find from the dropdown data i can add and write to that field
Please provide me some code + some pictures of your dropdown menu.
If i follow you right you have a filter system and if the value is not there what you searched for you want to enter it manually.
yes i want to enter mannually