Script ready checker

script_ready_check.js

function script_ready_check(script, cb, interval, limit){
    var time = 0;
    var check = setInterval(function(){
        if( typeof script !== 'undefined' ) {
            clearInterval(check);
            cb();
        }
        time += interval;
        if( time >= limit ) {
            clearInterval(check);
        }
    }, interval);
}