Searching multiple words in a string

Hi,

I've got this code in my AS3 :

var str:String = mySharedObject.data.theDate; 
var search:String = "monday"; 
var replace:String = "";  
function strReplace(str:String, search:String, replace:String😞String { 
return str.split(search).join(replace); 
}

Is it possible to tell the code to search for "monday or tuesday or wednsday, or thursday, or friday" and replace them with "_" ?

I would like to something like

var search:String ="tuesday","wednsday","thursday";

But it's not working..