Security when calling webservice from javascript

[Laddie]

Hi Guys, I have a doubt on how security is implemented when calling a webservice using javascript. My concern is that when the application is running in http any one can easily know which javascript function is called and which webservice function it is calling and the location of the service also. In this case how do you know if it comming from the right source or not ?. What are the ways security can be implemented in thie scenirio? Thank in advance for your advice.

Thanks Laddie Kindly rate if the answer was helpful