How can I execute Javascript before a JSF action is performed? [duplicate]

Answer 1

You can still use onclick. The JSF render kit specification (see Encode Behavior) describes how the link should handle it. Here is the important part (what it renders for onclick):

var a=function(){/*your onclick*/}; var b=function(){/*JSF onclick*/}; return (a()==false) ? false : b();

So your function wont be passed the event object (which isn't reliable cross browser anyway), but returning true/false will short-circuit the submission.

Answer 2

<h:commandLink id="myCommandLink" action="#{myPageCode.doDelete}">
    <h:outputText value="#{msgs.deleteText}" />
</h:commandLink>
<script type="text/javascript">
if (document.getElementById) {
    var commandLink = document.getElementById('<c:out value="${myPageCode.myCommandLinkClientId}" />');
    if (commandLink && commandLink.onclick) {
        var commandLinkOnclick = commandLink.onclick;
        commandLink.onclick = function() {
            var result = confirm('Do you really want to <c:out value="${msgs.deleteText}" />?');
            if (result) {
                return commandLinkOnclick();
            }
            return false;
        }
    }
}
</script>

Other Javascript actions (like validating form input etc) could be performed by replacing the call to confirm() with a call to another function.