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370 lines
11 KiB
370 lines
11 KiB
/*************************************************************
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*
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* Copyright (c) 2017-2020 The MathJax Consortium
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*=====================================================================*/
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(function () {
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/**
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* The various CDNs and their data for how to obtain versions
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*/
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var CDN = {
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'cdnjs.cloudflare.com': {
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api: 'https://api.cdnjs.com/libraries/mathjax?fields=version',
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key: 'version',
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base: 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/'
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},
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'rawcdn.githack.com': {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases/latest',
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key: 'tag_name',
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base: 'https://rawcdn.githack.com/mathjax/MathJax/'
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},
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'gitcdn.xyz': {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases/latest',
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key: 'tag_name',
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base: 'https://gitcdn.xyz/mathjax/MathJax/'
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},
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'cdn.statically.io': {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases/latest',
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key: 'tag_name',
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base: 'https://cdn.statically.io/gh/mathjax/MathJax/'
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},
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'unpkg.com': {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases/latest',
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key: 'tag_name',
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base: 'https://unpkg.com/mathjax@'
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},
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'cdn.jsdelivr.net': {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases/latest',
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key: 'tag_name',
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base: 'https://cdn.jsdelivr.net/npm/mathjax@'
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}
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};
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/**
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* The data for getting release versions from GitHub
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*/
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var GITHUB = {
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api: 'https://api.github.com/repos/mathjax/mathjax/releases',
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key: 'tag_name'
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};
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/**
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* The major version number for MathJax (we will load the highest version with this initial number)
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*/
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var MJX_VERSION = 2;
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/**
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* The name to use for the version in localStorage
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*/
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var MJX_LATEST = 'mjx-latest-version' + MJX_VERSION;
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/**
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* The amount of time a cached version number is valid
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*/
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var SAVE_TIME = 1000 * 60 * 60 * 24 * 7; // one week
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/**
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* Data for the script that loaded latest.js
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*/
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var script = null;
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/*=====================================================================*/
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/**
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* Produce an error message on the console
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*
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* @param {string} message The error message to display
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*/
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function Error(message) {
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if (console && console.error) {
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console.error('MathJax(latest.js): ' + message);
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}
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}
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/**
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* Create a ScriptData object from the given script tag and CDN
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*
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* @param {HTMLScriptElement} script The script tag whose data is desired
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* @param {CdnData} cdn The CDN data already obtained for the script (or null)
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* @return {ScriptData} The data for the given script
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*/
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function scriptData(script, cdn) {
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script.parentNode.removeChild(script);
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var src = script.src;
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var config = src.replace(/.*?\/latest\.js(\?|$)/, '$1');
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var data = (src.match(/(\d+\.\d+\.\d+)(\/unpacked)?\/latest.js\?/) || ['', '', '']);
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return {
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tag: script,
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src: src,
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id: script.id,
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version: data[1],
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unpacked: data[2] || '',
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config: config,
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cdn: cdn
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};
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}
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/**
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* Check if a script refers to MathJax on one of the CDNs
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*
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* @param {HTMLScriptElement} script The script tag to check
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* @return {boolean} True if the script is from a MathJax CDN
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*/
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function checkScript(script) {
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var CDNs = Object.keys(CDN);
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for (var i = 0, m = CDNs.length; i < m; i++) {
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var cdn = CDN[CDNs[i]];
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var url = cdn.base;
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var src = script.src;
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if (src && src.substr(0, url.length) === url && src.match(/\/latest\.js(\?|$)/)) {
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return scriptData(script, cdn);
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}
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}
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return null;
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}
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/**
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* @return {ScriptData} The data for the script tag that loaded latest.js
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*/
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function getScript() {
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if (document.currentScript) {
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return scriptData(document.currentScript);
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}
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var script = document.getElementById('MathJax-script');
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if (script && script.nodeName.toLowerCase() === 'script') {
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return checkScript(script);
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}
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var scripts = document.getElementsByTagName('script');
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for (var i = 0, m = scripts.length; i < m; i++) {
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var data = checkScript(scripts[i]);
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if (data) {
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return data;
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}
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}
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return null;
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}
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/*=====================================================================*/
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/**
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* Save the version and date information in localStorage so we don't
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* have to contact the CDN for every page that uses MathJax.
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*
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* @param {string} version The version to save
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*/
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function saveVersion(version) {
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try {
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var data = version + ' ' + Date.now();
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localStorage.setItem(MJX_LATEST, data);
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} catch (err) {}
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}
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/**
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* Get the version from localStorage, and make sure it is fresh enough to use
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*
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* @return {string|null} The version string (if one has been saved) or null (if not)
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*/
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function getSavedVersion() {
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try {
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var data = localStorage.getItem(MJX_LATEST).split(/ /);
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var version = data[0], date = data[0];
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if (date && Date.now() - parseInt(date) < SAVE_TIME) {
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return version;
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}
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} catch (err) {}
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return null;
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}
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/*=====================================================================*/
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/**
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* Create a script tag that loads the given URL
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*
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* @param {string} url The URL of the javascript file to be loaded
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* @param {string} id The id to use for the script tag
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*/
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function loadMathJax(url, id) {
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var script = document.createElement('script');
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script.type = 'text/javascript';
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script.async = true;
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script.src = url;
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if (id) {
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script.id = id;
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}
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var head = document.head || document.getElementsByTagName('head')[0] || document.body;
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if (head) {
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head.appendChild(script);
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} else {
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Error('Can\'t find the document <head> element');
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}
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}
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/**
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* When we can't find the current version, use the original URL but remove the "latest.js"
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*/
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function loadDefaultMathJax() {
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if (script) {
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loadMathJax(script.src.replace(/\/latest\.js/, '/MathJax.js'), script.id);
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} else {
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Error('Can\'t determine the URL for loading MathJax');
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}
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}
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/**
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* Load the given version using the base URL and file to load
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* (if the versions differ, run latest.js from the new version
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* in case there are important changes there)
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*
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* @param {string} version The version of MathJax to load from
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*/
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function loadVersion(version) {
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var file = 'MathJax.js' + script.config;
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if (script.version && script.version !== version) {
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file = 'latest.js' + script.config;
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}
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loadMathJax(script.cdn.base + version + script.unpacked + '/' + file, script.id);
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}
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/**
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* Check if the given version is acceptable and load it if it is.
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*
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* @param {string} version The version to check if it is the latest (valid) one
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* @return {boolean} True if it is the latest version, false if not
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*/
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function checkVersion(version) {
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var major = parseInt(version.split(/\./)[0]);
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if (major === MJX_VERSION && !version.match(/-(beta|rc)/)) {
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saveVersion(version);
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loadVersion(version);
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return true;
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}
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return false;
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}
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/*=====================================================================*/
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/**
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* Create an XMLHttpRequest object, if possible
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*
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* @return {XMLHttpRequest} The XMLHttpRequest instance
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*/
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function getXMLHttpRequest() {
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if (window.XMLHttpRequest) {
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return new XMLHttpRequest();
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}
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if (window.ActiveXObject) {
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try {return new window.ActiveXObject('Msxml2.XMLHTTP')} catch (err) {}
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try {return new window.ActiveXObject('Microsoft.XMLHTTP')} catch (err) {}
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}
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}
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/**
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* Request JSON data from a CDN. If it loads OK, call the action() function
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* on the data. If not, or if the action returns false, run the failure() function.
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*
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* @param {CdnData} cdn The CDN whose API will be used
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* @param {Function} action The function to perform when the data are received
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* @param {Function} failure The function to perform if data can't be obtained,
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* or if action() returns false
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*/
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function requestXML(cdn, action, failure) {
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var request = getXMLHttpRequest();
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if (request) {
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request.onreadystatechange = function () {
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if (request.readyState === 4) {
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if (request.status === 200) {
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!action(JSON.parse(request.responseText)) && failure();
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} else {
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Error('Problem acquiring MathJax version: status = ' + request.status);
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failure();
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}
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}
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};
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request.open('GET', cdn.api, true);
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request.send(null);
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} else {
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Error('Can\'t create XMLHttpRequest object');
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failure();
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}
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}
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/**
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* Look through the list of versions on GitHub and find the first one that
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* has the MJX_VERSION as its major version number, and load that. If none
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* is found, run the version from which latest.js was loaded.
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*/
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function loadLatestGitVersion() {
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requestXML(GITHUB, function (json) {
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if (!(json instanceof Array)) return;
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for (var i = 0, m = json.length; i < m; i++) {
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if (checkVersion(json[i][GITHUB.key])) {
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return true;
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}
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}
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return false;
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}, loadDefaultMathJax);
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}
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/**
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* Check the CDN for its latest version, and load that, if it is an
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* acceptable version, otherwise, (e.g., the current version has a
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* higher major version that MJX_VERSION), find the highest version on
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* GitHub with the given major version and use that. If one can't be
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* found, use the version where latest.js was loaded.
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*/
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function loadLatestCdnVersion() {
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requestXML(script.cdn, function (json) {
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if (json instanceof Array) {
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json = json[0];
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}
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if (!checkVersion(json[script.cdn.key])) {
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loadLatestGitVersion();
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}
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return true;
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}, loadDefaultMathJax);
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}
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/*=====================================================================*/
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/*
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* Find the script that loaded latest.js
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* If the script is from a known CDN:
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* Retrieve the cached version (if any)
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* Load the given version of the file, if the version is cached,
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* Otherwise find the latest version and load that.
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* Otherwise,
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* Load using the version where latest.js was loaded.
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*/
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script = getScript();
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if (script && script.cdn) {
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var version = getSavedVersion();
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version ?
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loadVersion(version) :
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loadLatestCdnVersion();
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} else {
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loadDefaultMathJax();
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}
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})();
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