Accessing a method inside a closure

Question

I'm trying to reference the method UTCDate() from another JS file that loads after this file bootstrap-datepicker.js. Is there a way for me to access this method. I tried using just UTCDate() I even tried window.UTCDate().

Here is the original file bootstrap-datepicker.js and they seem to be calling it directly inside the datePicker itself.

(function($, undefined){

    var $window = $(window);

    function UTCDate(){
        return new Date(Date.UTC.apply(Date, arguments));
    }
    function UTCToday(){
        var today = new Date();
        return UTCDate(today.getFullYear(), today.getMonth(), today.getDate());
    }
    function alias(method){
        return function(){
            return this[method].apply(this, arguments);
        };
    }

    var DateArray = (function(){
        var extras = {
            get: function(i){
                return this.slice(i)[0];
            },
            contains: function(d){
                // Array.indexOf is not cross-browser;
                // $.inArray doesn't work with Dates
                var val = d && d.valueOf();
                for (var i=0, l=this.length; i < l; i++)
                    if (this[i].valueOf() === val)
                        return i;
                return -1;
            },
            remove: function(i){
                this.splice(i,1);
            },
            replace: function(new_array){
                if (!new_array)
                    return;
                if (!$.isArray(new_array))
                    new_array = [new_array];
                this.clear();
                this.push.apply(this, new_array);
            },
            clear: function(){
                this.length = 0;
            },
            copy: function(){
                var a = new DateArray();
                a.replace(this);
                return a;
            }
        };

        return function(){
            var a = [];
            a.push.apply(a, arguments);
            $.extend(a, extras);
            return a;
        };
    })();

score 1 · Answer 1 · answered Aug 23 '14 at 15:19

That is how closures work: They close over variables.

function UTCDate(){
    return new Date(Date.UTC.apply(Date, arguments));
}

is private to your IIFE. You should better switch to The Revealing Module Pattern:

var myDateApp=function(){
    ...
    function UTCDate(){
        return new Date(Date.UTC.apply(Date, arguments));
    }
    ...

    return {
            ...
            UTCDate:UTCDate,
            ...
           };
}();

Then you could easily access the function UTCDate via myDateApp.UTCDate().

Or switch later on to AMD.

Thanks Thomas for the explanation how closures work. I'm wondering how the Datepicker itself is accessing the closure then. https://github.com/eternicode/bootstrap-datepicker/blob/master/js/bootstrap-datepicker.js — me-me, Aug 23 '14 at 15:25

score 0 · Accepted Answer · answered Aug 23 '14 at 15:10

0

You can't without modifying the code to export that method outside the anonymous closure.

answered Aug 23 '14 at 15:10

plalx

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If thats the case how are they calling it directly in this file. https://github.com/eternicode/bootstrap-datepicker/blob/master/js/bootstrap-datepicker.js – me-me Aug 23 '14 at 15:16
@ericb which line is it called outside the closure? – Thomas Junk Aug 23 '14 at 15:25
I believe 758, 779, 933 and multiple other areas. – me-me Aug 23 '14 at 15:27
@ericb The whole code you referenced all share the same top-level closure in which `UTCDate` is defined. Look carefully. – plalx Aug 23 '14 at 15:40
Ah you are right. So I guess there is no way to be able to get to it without altering the datepicker file itself. – me-me Aug 23 '14 at 15:45

Accessing a method inside a closure

2 Answers2