hx-sync

The hx-sync attribute allows you to synchronize AJAX requests between multiple elements.

The hx-sync attribute consists of a CSS selector to indicate the element to synchronize on, followed optionally by a colon and then by an optional syncing strategy. The available strategies are:

The queue modifier can take an additional argument indicating exactly how to queue:

Notes

This example resolves a race condition between a form's submit request and an individual input's validation request. Normally, without using hx-sync, filling out the input and immediately submitting the form triggers two parallel requests to /validate and /store. Using hx-sync="closest form:abort" on the input will watch for requests on the form and abort the input's request if a form request is present or starts while the input request is in flight.

<form hx-post="/store">
    <input id="title" name="title" type="text" 
        hx-post="/validate" 
        hx-trigger="change"
        hx-sync="closest form:abort">
    <button type="submit">Submit</button>
</form>

If you'd rather prioritize the validation request over the submit request, you can use the drop strategy. This example will prioritize the validation request over the submit request so that if a validation request is in flight, the form cannot be submitted.

<form hx-post="/store">
    <input id="title" name="title" type="text" 
        hx-post="/validate" 
        hx-trigger="change"
        hx-sync="closest form:drop"
    >
    <button type="submit">Submit</button>
</form>

When dealing with forms that contain many inputs, you can prioritize the submit request over all input validation requests using the hx-sync replace stragegy on the form tag. This will cancel any in-flight validation requests and issue only the hx-post="/store" request. If you'd rather abort the submit request and prioritize any existing validation requests you can use the hx-sync="this:abort" strategy on the form tag

<form hx-post="/store" hx-sync="this:replace">
    <input id="title" name="title" type="text" hx-post="/validate" hx-trigger="change" />
    <button type="submit">Submit</button>
</form>

When implementing active search functionality the hx-trigger attribute's delay modifier can be used to debounce the user's input and avoid making multiple requests while the user types. However, once a request is made, if the user begins typing again a new request will begin even if the previous one has not finished processing. This example will cancel any in-flight requests and use only the last request. In cases where the search input is contained within the target, then using hx-sync like this also helps reduce the chances that the input will be replaced while the user is still typing.

<input type="search" 
    hx-get="/search" 
    hx-trigger="keyup changed delay:500ms, search" 
    hx-target="#search-results"
    hx-sync="this:replace">