Dropdown search string to display results starting from the searched characters

Hi, how can I display only those results in dropdown whose starting character matches with the search string and not anywhere in the string.
Means… it should perform matching with search string from the start of the dropdown characters and not anywhere within the string…

E.g if I search : ‘Ca’ then only those options should come which starts with ‘ca’ and not such results like ‘zica’ as this contains ‘ca’.

Any thoughts on this?