gistfile1.js

// Templates:

param = { media: 'http://media.valvion.com/' };
url = "{media}logo.gif".supplant(param);

// Unfortunately, supplant method is not there in ES5 spec,
// so use the below prototype:

if (!String.prototype.supplant) {
    String.prototype.supplant = function (o) {
        return this.replace(/{([^{}]*)}/g,
            function (a, b) {
                var r = o[b];
                return typeof r === 'string' || 
                       typeof r === 'number' ? r : a;
            }
        );
    };
}