js实现string.format 字符串占位符

function StringFormat() ...{
         if (arguments.length == 0)
             return null;
         var str = arguments[0];
         for (var i = 1; i < arguments.length; i++) ...{
             var re = new RegExp('\\\\{' + (i - 1) + '\\\\}', 'gm');
             str = str.replace(re, arguments[i]);
         }
         return str;
}