According to the JavaScript documentation, the Regular Expression string search method returns either a boolean true of false value depending on a match being found. However, what is really returned is either the character position in the string where a match was found or a -1 if a match was not found. Thus, any JavaScript code expecting a boolean value return should instead use the Regular Expression string test method. Below is an example that should help illustrate this:

In both Netscape 4/6, the use of the global flag in a Regular Expression causes it to fail on subsequent usage. This is not a problem with Internet Explorer 5/6. For example, /abc/gi.exec("xxabcxx") succeeds the first time it’s used but fails if the same Regular Expression is used later, e.g., /abc/gi.exec("yyabcyy"). There does not appear to be a problem with the ignore flag.

A workaround is to use the Regular Expression constructor function and the compile method. This adds some overhead but it does work in all browsers. Below is an example of how this can be done.

function getRE(EXP) {
  var re = new RegExp();
  return re.compile(EXP, "gi");
}
  getRE("abc").exec("xxabcxx");
  getRE("abc").exec("yyabcyy");