How to execute a method passed as parameter to function

You can just call it as a normal function:

function myfunction(param1, callbackfunction)
{
    //do processing here
    callbackfunction();
}

The only extra thing is to mention context. If you want to be able to use the this keyword within your callback, you’ll have to assign it. This is frequently desirable behaviour. For instance:

function myfunction(param1, callbackfunction)
{
    //do processing here
    callbackfunction.call(param1);
}

In the callback, you can now access param1 as this. See Function.call.