onAvailable - Wait for libraries to be available in window and run a callback.

README.md

Use example:

onAvailable(['jQuery', 'jQuery.fn.countdown'], function() {
    jQuery('.countdown').countdown(the_countdown_date, function(event) {
        jQuery(this).html(event.strftime(the_countdown_template));
    });
});

onAvailable.js

function onAvailable(vars_to_check, callback, interval) {
    if (typeof vars_to_check === 'undefined' || typeof callback === 'undefined') {
        return;
    }
    //If vars_to_check is a scalar, make it as an array
    if (vars_to_check.constructor !== Array) {
        vars_to_check = [vars_to_check];
    }
    //Default interval 100ms
    if (typeof interval === 'undefined') {
        interval = 100;
    }
    var isDefined = function(s){
        s=s.split('.');
        var obj= window[s.shift()];
        while(obj && s.length) {
            obj=obj[s.shift()];
        }
        return (typeof obj !== 'undefined');
    };
    var intervals = '$_onAvailableIntervals';
    var callbacks = '$_onAvailableCallbacks';
    window[intervals] = window[intervals] || [];
    window[callbacks] = window[callbacks] || [];
    window[callbacks].push(callback);
    var index=window[callbacks].length - 1;
    window[intervals].push(setInterval(
        (function(index, vars) {
            return function() {
                var ready = true;
                for (var i = 0; i<vars.length; i++) {
                    ready = ready && isDefined(vars[i]);
                }
                if (ready) {
                    clearInterval(window[intervals][index]);
                    if (typeof window[callbacks][index] !== 'undefined') {
                        window[callbacks][index]();
                    }
                }
            }
        })(index, vars_to_check)
        , interval
    ));
}

onAvailable.min.js

function onAvailable(n,i,o){if(void 0!==n&&void 0!==i){n.constructor!==Array&&(n=[n]),void 0===o&&(o=100);var w=function(n){n=n.split(".");for(var i=window[n.shift()];i&&n.length;)i=i[n.shift()];return void 0!==i},r="$_onAvailableIntervals",t="$_onAvailableCallbacks";window[r]=window[r]||[],window[t]=window[t]||[],window[t].push(i);var a=window[t].length-1;window[r].push(setInterval(function(n,i){return function(){for(var o=!0,a=0;a<i.length;a++)o=o&&w(i[a]);o&&(clearInterval(window[r][n]),void 0!==window[t][n]&&window[t][n]())}}(a,n),o))}}