converting a string to regular expression

[swarnap]

I have to generate a regular expression dynamically to check the file extensions. The file extension types are stored in a model data which are are to be fetched in form of a string and set into an hidden variable.
<input type="hidden" id="extension" value="exe|doc" >

In javascript it is used as
var ext = document.getEle mentById("exten sion").value;
var regEx = /^.+\.(ext)$/i;

This does not replace the ext value "exe|doc" in the regEx .

If I'm using
var regEx = "/^.+\.("+ext+")$/i;
Then it is giving regEx = /^.+\.(exe|doc)$/i; but regEx is in string format.

So it is not working with "path.search(re gEx) != -1"
where path contains the name of the file.

So can anyone tell me how to generate a regular expression dynamically or say convert a string to regular expression.

[swarnap]

reg ex help

I want a regular expression such that it will not allow " and ' in a text.

[gchq]

I assume you mean search and replace?

I think what you want is:-

s/and/ /g

(the g is for 'global')