Where to put frontend javascript configuration variables

I ended up writing a conf.js file with content

window.CONFIG = {
    SOME_CONSTANT: 22,
}

and included it in a new <script> in my index.html before the other scripts. The window is not mandatory but shows where it comes from when I call that as window.CONFIG anywhere in the rest of the javascript.

CONFIG = (function(){  
var conf_info = {};
conf_info["url"] = 'http://codepen.io/pen/';
return{    
  getValue : function(param){
    return conf_info[param];
  }
}
})();

//some where in different file
document.getElementById("result").innerHTML = CONFIG.getValue('url');