SOURCE

function stringFormat(){
     if(arguments.length==0)
          return;
     var string = "a{0}b{1}";
     for(var i = 0 ; i < arguments.length;i++){
          var re = new RegExp('\\{'+ i +'\\}','gm');
          str = str.replace(re,arguments[i]);
     }
}

var name = "kitty"
stringFormat("hello{0}",name)