SingleFile/lib/hooks/hooks.js

/*
 * Copyright 2010-2019 Gildas Lormeau
 * contact : gildas.lormeau <at> gmail.com
 * 
 * This file is part of SingleFile.
 *
 *   The code in this file is free software: you can redistribute it and/or 
 *   modify it under the terms of the GNU Affero General Public License 
 *   (GNU AGPL) as published by the Free Software Foundation, either version 3
 *   of the License, or (at your option) any later version.
 * 
 *   The code in this file is distributed in the hope that it will be useful, 
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero 
 *   General Public License for more details.
 *
 *   As additional permission under GNU AGPL version 3 section 7, you may 
 *   distribute UNMODIFIED VERSIONS OF THIS file without the copy of the GNU 
 *   AGPL normally required by section 4, provided you include this license 
 *   notice and a URL through which recipients can access the Corresponding 
 *   Source.
 */

/* global history, dispatchEvent, CustomEvent, document, HTMLDocument */

this.hooks = this.hooks || (() => {

	if (document instanceof HTMLDocument) {
		const scriptElement = document.createElement("script");
		scriptElement.textContent = `(${hookPushState.toString()})()`;
		(document.documentElement || document).appendChild(scriptElement);
		scriptElement.remove();
	}

	return true;

	function hookPushState() {
		const pushState = history.pushState;
		let warningDisplayed;
		history.pushState = function (state, title, url) {
			if (!warningDisplayed) {
				warningDisplayed = true;
				console.warn("SingleFile is hooking the history.pushState API to detect navigation."); // eslint-disable-line no-console		
			}
			dispatchEvent(new CustomEvent("single-file-push-state", { detail: { state, title, url } }));
			pushState.call(history, state, title, url);
		};
	}

})();