How to call Apex class using java script

Apex Class:

global class ClassName{

 webService static String methodName(String camName) {

            Campaign cam = new Campaign(name = camName);

            return cam.name;

       }

}

Java Script:

var Campaign = sforce.sObject(“Campaign”);

var String = sforce.apex.exceute(“ClassName”,”methodName”,{name=”ABC”});