javascript - How to set default values in getURLParameter(name) function? -

i using following piece of code:

<script type="text/javascript">  function geturlparameter(name) { return decodeuricomponent((new regexp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search)||[,""])[1].replace(/\+/g, '%20'))||null;  }  </script> 

i use url parameter in jalert pop box follows:

<script> alert('warning', 'your'+geturlparameter('model') + 'is outdated.'); </script> 

how can specify if url parameter name example, "generic" or "undefined", set default parameter?

thanks

this checks whether name param set or not; if not, gets default value:

function geturlparameter(name) {      if (!name)         name = 'default value';      return decodeuricomponent((new regexp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search)||[,""])[1].replace(/\+/g, '%20'))||null; }