refactor: split out logic to determine ajaxification into exported method

There was some internal logic in ajaxify that handled special links that
should explicitly not be ajaxified (either it is a null href or should be
loaded as a direct page load, etc.) - this was moved out to an exported
method so it can be consumed by the service worker onmessage listener.

Also since this logic evolved over many years, there were some
duplications and so those have been amended (though I will not guarantee
that it was done bug/regression free!!)

public/src/ajaxify.js

@@ -23,6 +23,60 @@ ajaxify.widgets = { render: render };
 	if ('scrollRestoration' in history) {
 		history.scrollRestoration = 'manual';
 	}
+
+	ajaxify.check = (item) => {
+		/**
+		 * returns:
+		 *   true  (ajaxify OK)
+		 *   false (browser default)
+		 *   null  (no action)
+		 */
+		let urlObj;
+		let pathname;
+		try {
+			urlObj = new URL(item, `${document.location.origin}${config.relative_path}`);
+			({ pathname } = urlObj);
+		} catch (e) {
+			return false;
+		}
+
+		const internalLink = utils.isInternalURI(urlObj, window.location, config.relative_path);
+		// eslint-disable-next-line no-script-url
+		const hrefEmpty = href => href === undefined || href === '' || href === 'javascript:;';
+
+		if (item instanceof Element && item.getAttribute('data-ajaxify') === 'false') {
+			if (!internalLink) {
+				return;
+			}
+
+			return null;
+		}
+
+		// Default behaviour for rss feeds
+		if (internalLink && pathname.endsWith('.rss')) {
+			return false;
+		}
+
+		// Default behaviour for sitemap
+		if (internalLink && String(pathname).startsWith(config.relative_path + '/sitemap') && pathname.endsWith('.xml')) {
+			return false;
+		}
+
+		// Default behaviour for uploads and direct links to API urls
+		if (internalLink && ['/uploads', '/assets/', '/api/'].some(function (prefix) {
+			return String(pathname).startsWith(config.relative_path + prefix);
+		})) {
+			return false;
+		}
+
+		// eslint-disable-next-line no-script-url
+		if (hrefEmpty(urlObj.href) || urlObj.protocol === 'javascript:' || pathname === '#' || pathname === '') {
+			return null;
+		}
+
+		return true;
+	};
+
 	ajaxify.go = function (url, callback, quiet) {
 		// Automatically reconnect to socket and re-ajaxify on success
 		if (!socket.connected && parseInt(app.user.uid, 10) >= 0) {
@@ -512,10 +566,6 @@ $(document).ready(function () {
 	});
 
 	function ajaxifyAnchors() {
-		function hrefEmpty(href) {
-			// eslint-disable-next-line no-script-url
-			return href === undefined || href === '' || href === 'javascript:;';
-		}
 		const location = document.location || window.location;
 		const rootUrl = location.protocol + '//' + (location.hostname || location.host) + (location.port ? ':' + location.port : '');
 		const contentEl = document.getElementById('content');
@@ -527,9 +577,7 @@ $(document).ready(function () {
 				return;
 			}
 
-			const href = this.pathname;
 			const internalLink = utils.isInternalURI(this, window.location, config.relative_path);
-
 			const rootAndPath = new RegExp(`^${rootUrl}${config.relative_path}/?`);
 			const process = function () {
 				if (!e.ctrlKey && !e.shiftKey && !e.metaKey && e.which === 1) {
@@ -560,52 +608,36 @@ $(document).ready(function () {
 				}
 			};
 
-			if (this.getAttribute('data-ajaxify') === 'false') {
+			const check = ajaxify.check(this);
-				if (!internalLink) {
+			switch (check) {
-					return;
+				case true: {
-				}
+					if (app.flags && app.flags.hasOwnProperty('_unsaved') && app.flags._unsaved === true) {
-				return e.preventDefault();
+						if (e.ctrlKey) {
-			}
+							return;
-
-			// Default behaviour for rss feeds
-			if (internalLink && href && href.endsWith('.rss')) {
-				return;
-			}
-
-			// Default behaviour for sitemap
-			if (internalLink && href && String(_self.pathname).startsWith(config.relative_path + '/sitemap') && href.endsWith('.xml')) {
-				return;
-			}
-
-			// Default behaviour for uploads and direct links to API urls
-			if (internalLink && ['/uploads', '/assets/', '/api/'].some(function (prefix) {
-				return String(_self.pathname).startsWith(config.relative_path + prefix);
-			})) {
-				return;
-			}
-
-			// eslint-disable-next-line no-script-url
-			if (hrefEmpty(this.href) || this.protocol === 'javascript:' || href === '#' || href === '') {
-				return e.preventDefault();
-			}
-
-			if (app.flags && app.flags.hasOwnProperty('_unsaved') && app.flags._unsaved === true) {
-				if (e.ctrlKey) {
-					return;
-				}
-
-				require(['bootbox'], function (bootbox) {
-					bootbox.confirm('[[global:unsaved-changes]]', function (navigate) {
-						if (navigate) {
-							app.flags._unsaved = false;
-							process.call(_self);
 						}
-					});
-				});
-				return e.preventDefault();
-			}
 
-			process.call(_self);
+						require(['bootbox'], function (bootbox) {
+							bootbox.confirm('[[global:unsaved-changes]]', function (navigate) {
+								if (navigate) {
+									app.flags._unsaved = false;
+									process.call(_self);
+								}
+							});
+						});
+						return e.preventDefault();
+					}
+
+					process.call(_self);
+					break;
+				}
+
+				case null: {
+					e.preventDefault();
+					break;
+				}
+
+				// default is default browser behaviour
+			}
 		});
 	}