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