Question

I’m tring to get some json to contain a function so that the option in the plugin gets the returned value of the function that was in the json string.

The set up is as such:

default.txt

    [
        {
            "element":"a[href$='.jpg']",
            "options":{
                "label":"test"
                }
        },{
            "element":"a#hover",
            "options":{
                "label":(function(ele){ return 'test'; })()
            }
        }
    ]

and the plug-in is

(function($) {
    function defined(obj){return typeof(obj)!=='undefined';}
    function evaluate(ele, obj) {
        if(typeof obj === 'function') {
            //alert('is function');
            obj = obj(ele);
        }else{
            try{
                //alert('thinking it may be a function still');
                obj = eval("("+obj+"("+ele+"));"); 
                //obj = (obj)(ele);
            }catch(err){
                //Handle errors here
                //alert('not function');
            }
        }
        return obj;
    }
    function debug(message) {
          console.debug(message);
    }
    $.set = function(options){
        var settings = $.extend({}, {}, options);
        if(defined(settings.actions)){
            $.each(settings.actions, function(index, value) { 
                $(value.element).do_action(defined(value.options)?value.options:null);
            });
        }   
    }

  $.fn.do_action = function(options) {
    // Add event handler to all matching elements
    return this.each(function() {
        var ele = $(this);
            var settings = $.extend({}, $.fn.do_action.defaults, options);
            var label= evaluate(ele, settings.label);

            var message = "label:'" + label + "'";
            debug('Tracking ' + action + ' ' + message);
    });
  };
  $.fn.do_action.defaults = {
    label         : function(ele) { return ele.attr('href'); }
  };
}(jQuery));

and the control is

$.getJSON('default.txt' , function(data){
    $.set({
        actions:data // this si where we pull in the options
    });
});

I seems to work if I put in an alert inside the anonymous function, so from

"label":(function(ele){ return 'test'; })()

to

"label":(function(ele){ alert('test') })()

but after that I can’t seem to get it to print right in the console as I only get the message

Tracking label:'(function(ele){ return 'test'; })

[EDIT]
Please stop saying that “you should not put code in json”. If you work for Google and are their top level programmers getting paid the big super bucks then I’ll listen to the why’s, but I’m sorry if it’s good for them, it’ll work for me. Don’t know what else to say, I already understand the point of why you should avoid it which I aim to do as well. There are times when you just can’t and why i supect Google does the same.

Answer 1

Your label member is not a function; it’s a value returned by a function. The final () at the end means “execute this function immediate whenever the value of label is requested and provide its return value as the value of label“.

That said, if you must include functions in your JSON object (and from what you’ve said, you do) your best bet is to stringify-and-eval your functions. You should also be able to use raw functions in your JSON, like {foo : (function(){ … }) }, though I’ve personally had a tricky time getting this right (but that’s just me — if you can get it right, go for it).

(As an aside, it’s not possible to stringify functions from existing objects, but if you’re getting your functions as text from user/programmer input, that’s not an issue.)