feat: add double width char checker

Author: hotoo

tools/double-width-char.js

@@ -0,0 +1,30 @@
+function findLengthGreaterThanOneHanChars(str) {
+  const result = new Set();
+
+  // 使用 for...of 遍历，可以正确处理代理对字符（即长度为2的字符）
+  for (const char of str) {
+    // 判断长度（代码单元长度），大于1即是代理对字符
+    if (char.length > 1) {
+      // 判断是否是汉字（补充平面的范围一般在U+20000至U+2FA1F）
+      const codePoint = char.codePointAt(0);
+      if (
+        (codePoint >= 0x20000 && codePoint <= 0x2A6DF) ||  // CJK Unified Ideographs Extension B
+        (codePoint >= 0x2A700 && codePoint <= 0x2B73F) ||  // CJK Unified Ideographs Extension C
+        (codePoint >= 0x2B740 && codePoint <= 0x2B81F) ||  // CJK Unified Ideographs Extension D
+        (codePoint >= 0x2B820 && codePoint <= 0x2CEAF) ||  // CJK Unified Ideographs Extension E
+        (codePoint >= 0x2CEB0 && codePoint <= 0x2EBEF)     // CJK Unified Ideographs Extension F
+      ) {
+        result.add(char);
+      }
+    }
+  }
+
+  return Array.from(result);
+}
+
+// 测试字符串中含有常见和补充区汉字
+const testStr = "汉字𠀀𠂢𠃌常见字和补充区字混合𠄀𠆢";
+console.log("测试字符串:", testStr.length);
+const found = findLengthGreaterThanOneHanChars(testStr);
+
+console.log(found);