Question

I have the following method added to an object :

loadAPIServiceData : function(service, format, term, callback) {
        return $.when($.ajax({
            url: service + ((term) ? term : '') + '?format=' + format
        })).done(function(result) {
            return callback.apply(result, [ result ]);
        });
    },

The callback function is passed one parameter that I need further down in the chain when I’m loading the data ( the result obviously gets whatever I get back from the AJAX call ). What I need is to be able to add more parameters to the callback function when it’s called, and still have the result in there 🙂

To be more explicit about it this is what I was meaning when I said “I need is to be able to add more parameters to the callback function when it’s called, and still have the result in there” :

var test = loadAPIServiceData('some_service', 'json', 'some_term', function(result, another_parameter, ...) {

});

Answer 1

You can use bind for apply arguments without need to modify the loadAPIServiceData:

function myCallback(arg1, arg2, result) {
    //
}

loadAPIServiceData(service, format, term, myCallback.bind(this, arg1, arg2));

If you prefer keep result in first arg position, this code send all additional argument to the callback, using the arguments object:

loadAPIServiceData : function(service, format, term, callback) {
    var add_args = Array.prototype.slice.call(arguments, 4);

    return $.when($.ajax({
        url: service + ((term) ? term : '') + '?format=' + format
    })).done(function(result) {
        return callback.apply(this, result, [ result].concat(add_args));
    });
},

function myCallback(result, arg1, arg2) {
    //
}

loadAPIServiceData(service, format, term, myCallback, "arg1", "arg2");