flow like the river

BACK_BACK/node_modules/htmlnano/lib/modules/removeRedundantAttributes.js

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+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = removeRedundantAttributes;
+exports.redundantScriptTypes = void 0;
+// https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types#JavaScript_types
+const redundantScriptTypes = new Set(['application/javascript', 'application/ecmascript', 'application/x-ecmascript', 'application/x-javascript', 'text/javascript', 'text/ecmascript', 'text/javascript1.0', 'text/javascript1.1', 'text/javascript1.2', 'text/javascript1.3', 'text/javascript1.4', 'text/javascript1.5', 'text/jscript', 'text/livescript', 'text/x-ecmascript', 'text/x-javascript']);
+exports.redundantScriptTypes = redundantScriptTypes;
+const redundantAttributes = {
+  'form': {
+    'method': 'get'
+  },
+  'input': {
+    'type': 'text'
+  },
+  'button': {
+    'type': 'submit'
+  },
+  'script': {
+    'language': 'javascript',
+    'type': node => {
+      for (const [attrName, attrValue] of Object.entries(node.attrs)) {
+        if (attrName.toLowerCase() !== 'type') {
+          continue;
+        }
+
+        return redundantScriptTypes.has(attrValue);
+      }
+
+      return false;
+    },
+    // Remove attribute if the function returns false
+    'charset': node => {
+      // The charset attribute only really makes sense on “external” SCRIPT elements:
+      // http://perfectionkills.com/optimizing-html/#8_script_charset
+      return node.attrs && !node.attrs.src;
+    }
+  },
+  'style': {
+    'media': 'all',
+    'type': 'text/css'
+  },
+  'link': {
+    'media': 'all',
+    'type': node => {
+      // https://html.spec.whatwg.org/multipage/links.html#link-type-stylesheet
+      let isRelStyleSheet = false;
+      let isTypeTextCSS = false;
+
+      if (node.attrs) {
+        for (const [attrName, attrValue] of Object.entries(node.attrs)) {
+          if (attrName.toLowerCase() === 'rel' && attrValue === 'stylesheet') {
+            isRelStyleSheet = true;
+          }
+
+          if (attrName.toLowerCase() === 'type' && attrValue === 'text/css') {
+            isTypeTextCSS = true;
+          }
+        }
+      } // Only "text/css" is redudant for link[rel=stylesheet]. Otherwise "type" shouldn't be removed
+
+
+      return isRelStyleSheet && isTypeTextCSS;
+    }
+  },
+  // See: https://html.spec.whatwg.org/#lazy-loading-attributes
+  'img': {
+    'loading': 'eager'
+  },
+  'iframe': {
+    'loading': 'eager'
+  }
+};
+const tagsHaveRedundantAttributes = new Set(Object.keys(redundantAttributes));
+/** Removes redundant attributes */
+
+function removeRedundantAttributes(tree) {
+  tree.walk(node => {
+    if (!node.tag) {
+      return node;
+    }
+
+    if (!tagsHaveRedundantAttributes.has(node.tag)) {
+      return node;
+    }
+
+    const tagRedundantAttributes = redundantAttributes[node.tag];
+    node.attrs = node.attrs || {};
+
+    for (const redundantAttributeName of Object.keys(tagRedundantAttributes)) {
+      let tagRedundantAttributeValue = tagRedundantAttributes[redundantAttributeName];
+      let isRemove = false;
+
+      if (typeof tagRedundantAttributeValue === 'function') {
+        isRemove = tagRedundantAttributeValue(node);
+      } else if (node.attrs[redundantAttributeName] === tagRedundantAttributeValue) {
+        isRemove = true;
+      }
+
+      if (isRemove) {
+        delete node.attrs[redundantAttributeName];
+      }
+    }
+
+    return node;
+  });
+  return tree;
+}