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if (htmx.version && !htmx.version.startsWith("1.")) {
console.warn("WARNING: You are using an htmx 1 extension with htmx " + htmx.version +
". It is recommended that you move to the version of this extension found on https://htmx.org/extensions")
}
// This adds the "preload" extension to htmx. By default, this will
// preload the targets of any tags with `href` or `hx-get` attributes
// if they also have a `preload` attribute as well. See documentation
// for more details
htmx.defineExtension("preload", {
onEvent: function(name, event) {
// Only take actions on "htmx:afterProcessNode"
if (name !== "htmx:afterProcessNode") {
return;
}
// SOME HELPER FUNCTIONS WE'LL NEED ALONG THE WAY
// attr gets the closest non-empty value from the attribute.
var attr = function(node, property) {
if (node == undefined) {return undefined;}
return node.getAttribute(property) || node.getAttribute("data-" + property) || attr(node.parentElement, property)
}
// load handles the actual HTTP fetch, and uses htmx.ajax in cases where we're
// preloading an htmx resource (this sends the same HTTP headers as a regular htmx request)
var load = function(node) {
// Called after a successful AJAX request, to mark the
// content as loaded (and prevent additional AJAX calls.)
var done = function(html) {
if (!node.preloadAlways) {
node.preloadState = "DONE"
}
if (attr(node, "preload-images") == "true") {
document.createElement("div").innerHTML = html // create and populate a node to load linked resources, too.
}
}
return function() {
// If this value has already been loaded, then do not try again.
if (node.preloadState !== "READY") {
return;
}
// Special handling for HX-GET - use built-in htmx.ajax function
// so that headers match other htmx requests, then set
// node.preloadState = TRUE so that requests are not duplicated
// in the future
var hxGet = node.getAttribute("hx-get") || node.getAttribute("data-hx-get")
if (hxGet) {
htmx.ajax("GET", hxGet, {
source: node,
handler:function(elt, info) {
done(info.xhr.responseText);
}
});
return;
}
// Otherwise, perform a standard xhr request, then set
// node.preloadState = TRUE so that requests are not duplicated
// in the future.
if (node.getAttribute("href")) {
var r = new XMLHttpRequest();
r.open("GET", node.getAttribute("href"));
r.onload = function() {done(r.responseText);};
r.send();
return;
}
}
}
// This function processes a specific node and sets up event handlers.
// We'll search for nodes and use it below.
var init = function(node) {
// If this node DOES NOT include a "GET" transaction, then there's nothing to do here.
if (node.getAttribute("href") + node.getAttribute("hx-get") + node.getAttribute("data-hx-get") == "") {
return;
}
// Guarantee that we only initialize each node once.
if (node.preloadState !== undefined) {
return;
}
// Get event name from config.
var on = attr(node, "preload") || "mousedown"
const always = on.indexOf("always") !== -1
if (always) {
on = on.replace('always', '').trim()
}
// FALL THROUGH to here means we need to add an EventListener
// Apply the listener to the node
node.addEventListener(on, function(evt) {
if (node.preloadState === "PAUSE") { // Only add one event listener
node.preloadState = "READY"; // Required for the `load` function to trigger
// Special handling for "mouseover" events. Wait 100ms before triggering load.
if (on === "mouseover") {
window.setTimeout(load(node), 100);
} else {
load(node)() // all other events trigger immediately.
}
}
})
// Special handling for certain built-in event handlers
switch (on) {
case "mouseover":
// Mirror `touchstart` events (fires immediately)
node.addEventListener("touchstart", load(node));
// WHhen the mouse leaves, immediately disable the preload
node.addEventListener("mouseout", function(evt) {
if ((evt.target === node) && (node.preloadState === "READY")) {
node.preloadState = "PAUSE";
}
})
break;
case "mousedown":
// Mirror `touchstart` events (fires immediately)
node.addEventListener("touchstart", load(node));
break;
}
// Mark the node as ready to run.
node.preloadState = "PAUSE";
node.preloadAlways = always;
htmx.trigger(node, "preload:init") // This event can be used to load content immediately.
}
// Search for all child nodes that have a "preload" attribute
event.target.querySelectorAll("[preload]").forEach(function(node) {
// Initialize the node with the "preload" attribute
init(node)
// Initialize all child elements that are anchors or have `hx-get` (use with care)
node.querySelectorAll("a,[hx-get],[data-hx-get]").forEach(init)
})
}
})
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