​

    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;

                }

            );

        };

    }

​

​

​

var spanTmpl=  '<span id="{id}"></span>';

​

​

var a= spanTmpl.supplant({id:"js"});

var b= spanTmpl.supplant({id:"bla"});

​

console.log(a); //<span id="js"></span> 

console.log(b);//<span id="bla"></span> 

​