flow like the river

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

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+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = collapseAttributeWhitespace;
+
+var _collapseAttributeWhitespace = require("./collapseAttributeWhitespace");
+
+/** Deduplicate values inside list-like attributes (e.g. class, rel) */
+function collapseAttributeWhitespace(tree) {
+  tree.walk(node => {
+    if (!node.attrs) {
+      return node;
+    }
+
+    Object.keys(node.attrs).forEach(attrName => {
+      const attrNameLower = attrName.toLowerCase();
+
+      if (!_collapseAttributeWhitespace.attributesWithLists.has(attrNameLower)) {
+        return;
+      }
+
+      const attrValues = node.attrs[attrName].split(/\s/);
+      const uniqeAttrValues = new Set();
+      const deduplicatedAttrValues = [];
+      attrValues.forEach(attrValue => {
+        if (!attrValue) {
+          // Keep whitespaces
+          deduplicatedAttrValues.push('');
+          return;
+        }
+
+        if (uniqeAttrValues.has(attrValue)) {
+          return;
+        }
+
+        deduplicatedAttrValues.push(attrValue);
+        uniqeAttrValues.add(attrValue);
+      });
+      node.attrs[attrName] = deduplicatedAttrValues.join(' ');
+    });
+    return node;
+  });
+  return tree;
+}