Search Page For String Within HREF

I need javascript code that will search all the links on the page and then search for a string value within the href.

Here is an example of the link: <a href="http://www.sample.com/index.jsp?UserIDExample=1111111">

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Here was my failed attempt:

            if ( document.getElementsByTagName('a').href.indexOf("UserIDExample") > -1 ) {
                        alert("found");
                  else
                        alert("not found);
            }