javascript render template

function render(tpl,data){
    var matches = tpl.match(/{[^\}]+}/g);
    for(var i in matches){
        var rep =   eval("data."+matches[i].replace('{','').replace('}',''));
        tpl = tpl.replace(matches[i],rep);
    }
    return tpl;
  }
 alert(render("{a} is all that i've {b.a} {b.b} {b.c}", {a:"this", b:{a:"ever",b:"really",c:"needed"}}))