asmx authentication

Question

I have an asmx webservice that contains functions of Insert, delete, update, select, I am consuming it via ajax, because my application cannot work on the server side. My question is how can I provide authentication to connect to this webservice? I even put Login and password in each function but in javascript and html there is no way to hide this password, I will have to pass via parameters to access and then who see the page code can see the login and password. Searching the stack I found this link https://stackoverflow.com/questions/4734397/using-an-oauth-access-token-to-access-soap-service, but I could not understand its operation inside my webservice

Answer 1

After researching, I understood that asmx is obsolete, miscrosoft leaves this option in Visual Studio only because it is 'legacy', I am developing in Webapi which is very simple and with many more options. I found this site that talks about security in Restful, and cites the options that we can use to implement this (in clear Web Api), very enlightening:

http://blog.rivendel.com.br/2013/06/07/seguranca-em-apis-rest-parte-1/