HX-Trigger Response Headers

These response headers can be used to trigger client side actions on the target element within a response to htmx. You can trigger a single event or as many uniquely named events as you would like.

The headers are:

HX-Trigger - trigger events as soon as the response is received.
HX-Trigger-After-Settle - trigger events after the settling step.
HX-Trigger-After-Swap - trigger events after the swap step.

To trigger a single event with no additional details you can simply send the event name in a header like so:

HX-Trigger: myEvent

This will trigger myEvent on the triggering element and will bubble up to the body. As an example you could listen for this event like this:

document.body.addEventListener("myEvent", function(evt){
    alert("myEvent was triggered!");
})

… or like this, if you’re trying to trigger some element without using JS code:

<!-- Since it bubbles up to the <body>, we must use the `from:body` modifier below -->
<div hx-trigger="myEvent from:body" hx-get="/example"></div>

If you want to pass details along with the event, you can move to JSON for the value of the trigger:

HX-Trigger: {"showMessage":"Here Is A Message"}

To handle this event you would write the following code:

document.body.addEventListener("showMessage", function(evt){
    alert(evt.detail.value);
})

Note that the value of the message was put into the detail.value slot. If you wish to pass multiple pieces of data you can use a nested JSON object on the right hand side of the JSON object:

HX-Trigger: {"showMessage":{"level" : "info", "message" : "Here Is A Message"}}

And handle this event like so:

document.body.addEventListener("showMessage", function(evt){
   if(evt.detail.level === "info"){
     alert(evt.detail.message);   
   }
})

Each property of the JSON object on the right hand side will be copied onto the details object for the event.

Targetting Other Elements

You can trigger events on other target elements by adding a target argument to the JSON object.

HX-Trigger: {"showMessage":{"target" : "#otherElement"}}

Multiple Triggers

If you wish to invoke multiple events, you can simply add additional properties to the top level JSON object:

HX-Trigger: {"event1":"A message", "event2":"Another message"}

You may also trigger multiple events with no additional details by sending event names separated by commas, like so:

HX-Trigger: event1, event2

Using events gives you a lot of flexibility to add functionality to normal htmx responses.