Feel free to test JavaScript’s RegExp support right here in your browser. Obviously, JavaScript will need to be enabled in your browser for this to work. Since this tester is implemented in JavaScript, it will reflect the features and limitations of your web browser’s JavaScript implementation. If you’re looking for a general-purpose regular expression tester supporting all the regex flavors that matter then grab yourself a copy of RegexBuddy.

Learn how to use the JavaScript RegExp object.

JavaScript RegExp Tester Source Code

<SCRIPT LANGUAGE="JavaScript"><!--
function demoMatchClick() {
  var re = new RegExp(document.demoMatch.regex.value);
  if (document.demoMatch.subject.value.match(re)) {
    alert("Successful match");
  } else {
    alert("No match");
  }
}

function demoShowMatchClick() {
  var re = new RegExp(document.demoMatch.regex.value);
  var m = re.exec(document.demoMatch.subject.value);
  if (m == null) {
    alert("No match");
  } else {
    var s = "Match at position " + m.index + ":\n";
    for (i = 0; i < m.length; i++) {
      s = s + m[i] + "\n";
    }
    alert(s);
  }
}

function demoReplaceClick() {
  var re = new RegExp(document.demoMatch.regex.value, "g");
  document.demoMatch.result.value =
    document.demoMatch.subject.value.replace(re,
      document.demoMatch.replacement.value);
}
// -->
</SCRIPT>

<FORM ID="demoMatch" NAME="demoMatch" METHOD=POST ACTION="javascript:void(0)">
<P>Regexp: <INPUT TYPE=TEXT NAME="regex" VALUE="\bt[a-z]+\b" SIZE=50></P>
<P>Subject string: <INPUT TYPE=TEXT NAME="subject"
   VALUE="This is a test of the JavaScript RegExp object" SIZE=50></P>
<P><INPUT TYPE=SUBMIT VALUE="Test Match" ONCLICK="demoMatchClick()">
<INPUT TYPE=SUBMIT VALUE="Show Match" ONCLICK="demoShowMatchClick()"></P>

<P>Replacement text: <INPUT TYPE=TEXT NAME="replacement" VALUE="replaced" SIZE=50></P>
<P>Result: <INPUT TYPE=TEXT NAME="result"
   VALUE="click the button to see the result" SIZE=50></P>
<P><INPUT TYPE=SUBMIT VALUE="Replace" ONCLICK="demoReplaceClick()"></P>
</FORM>