update sharepoint list using javascript

i have below requirement and i do not know how to write the javascript function to update in sharepoint list:

Basic ui:

Name:(Text box)

Id:(dropdown box)

Area interetested:(one checkbox)

submit button

when i click the above submit button it should update the list item with name,id,area interested. i do not know how to bind the dropdown box values and checkbox values using javascript also how to update the sharepoint list item

Blitz