How to call Salesforce Apex class using javascript?

Check the below code.

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”});