add excerpt shortcode

_config/shortcodes.js

@@ -0,0 +1,30 @@
+const seperator = {
+    start: '<!-- excerpt start -->',
+    end: '<!-- excerpt end -->',
+    total: '<!-- excerpt -->'
+};
+
+module.exports = function (eleventyConfig) {
+    // excerpt shortcode for feed layouts
+    // taken from https://github.com/brob/eleventy-plugin-blog-tools
+    eleventyConfig.addShortcode("excerpt", function (article) {
+        let excerpt = article.data.excerpt ? `<p>${article.data.excerpt}</p>` : "";
+        const articleContent = article.templateContent;
+
+        let startPosition = articleContent.toLowerCase().indexOf(seperator.start);
+        let endPosition = articleContent.toLowerCase().indexOf(seperator.end);
+        let totalPosition = articleContent.toLowerCase().indexOf(seperator.total)
+
+        if (totalPosition !== -1) {
+            excerpt = articleContent.substring(0, totalPosition);
+        } else if (startPosition !== -1 && endPosition !== -1) {
+            excerpt = articleContent.substring(startPosition + seperator.start.length, endPosition);
+        } else if (!article.data.excerpt) {
+            let startPosition = articleContent.toLowerCase().indexOf('<p>');
+            let endPosition = articleContent.toLowerCase().indexOf('</p>');
+
+            excerpt = articleContent.substring(startPosition + 3, endPosition);
+        }
+        return excerpt
+    });
+};

eleventy.config.js

@@ -5,6 +5,7 @@ const toml = require("@iarna/toml");
 const addDateParsing = require("./_config/date");
 const addFilters = require("./_config/filters");
 const addPlugins = require("./_config/plugins");
+const addShortcodes = require("./_config/shortcodes");
 
 module.exports = function (eleventyConfig) {
     let siteData;
@@ -28,6 +29,7 @@ module.exports = function (eleventyConfig) {
     addDateParsing(eleventyConfig, { TIME_ZONE: siteData.timezone });
     addFilters(eleventyConfig, { TIME_ZONE: siteData.timezone, defaultLanguage: siteData.default_language });
     addPlugins(eleventyConfig, { defaultLanguage: siteData.default_language });
+    addShortcodes(eleventyConfig);
 
     return {
         markdownTemplateEngine: "njk",