how to set a passed function in javascript
===

I am creating a new object variable and passing an object as an argument: 

    var obj = new test({
		first : $('#fname').val(),
		last : $('#lname').val(),
		fn : function() {
			alert(this.first + " " + this.last);
		}
	});

This is the called function when creating the above variable:

    var test = function(obj) {
        this.fn = function() {
            alert("No custom function was made.");
        }
	
        this.first = obj.first;
        this.last = obj.last;
        if(obj.fn)
            this.fn = obj.fn(); //I also tried it without the '()' after 'obj.fn'
    };

The first and last variables are fine, but I cannot figure out how to get the custom function that is passed to be set.