diff --git a/app/src/main/java/io/legado/app/help/JsExtensions.java b/app/src/main/java/io/legado/app/help/JsExtensions.java
deleted file mode 100644
index 7b45b0bc2..000000000
--- a/app/src/main/java/io/legado/app/help/JsExtensions.java
+++ /dev/null
@@ -1,55 +0,0 @@
-package io.legado.app.help;
-
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-import io.legado.app.model.analyzeRule.AnalyzeUrl;
-import io.legado.app.utils.Encoder;
-import io.legado.app.utils.StringUtils;
-import retrofit2.Call;
-import retrofit2.Response;
-
-public class JsExtensions {
-
-
-    /**
-     * js实现跨域访问,不能删
-     */
-    public String ajax(String urlStr) {
-        try {
-            AnalyzeUrl analyzeUrl = new AnalyzeUrl(urlStr, null, null, null, null, null);
-            Call call = analyzeUrl.getResponse();
-            Response response = call.execute();
-            if (response.body() != null) {
-                return response.body().toString();
-            }
-        } catch (Exception e) {
-            return e.getLocalizedMessage();
-        }
-        return null;
-    }
-
-    /**
-     * js实现解码,不能删
-     */
-    public String base64Decoder(String str) {
-        return Encoder.INSTANCE.base64Decoder(str);
-    }
-
-    /**
-     * 章节数转数字
-     */
-    public String toNumChapter(String s) {
-        if (s == null) {
-            return null;
-        }
-        Pattern pattern = Pattern.compile("(第)(.+?)(章)");
-        Matcher matcher = pattern.matcher(s);
-        if (matcher.find()) {
-            return matcher.group(1) + StringUtils.INSTANCE.stringToInt(matcher.group(2)) + matcher.group(3);
-        } else {
-            return s;
-        }
-    }
-
-}
diff --git a/app/src/main/java/io/legado/app/help/JsExtensions.kt b/app/src/main/java/io/legado/app/help/JsExtensions.kt
new file mode 100644
index 000000000..238996a5a
--- /dev/null
+++ b/app/src/main/java/io/legado/app/help/JsExtensions.kt
@@ -0,0 +1,53 @@
+package io.legado.app.help
+
+import io.legado.app.model.analyzeRule.AnalyzeUrl
+import io.legado.app.utils.Encoder
+import io.legado.app.utils.StringUtils
+import java.util.regex.Pattern
+
+
+@Suppress("unused")
+class JsExtensions {
+
+    /**
+     * js实现跨域访问,不能删
+     */
+    fun ajax(urlStr: String): String? {
+        try {
+            val analyzeUrl = AnalyzeUrl(urlStr, null, null, null, null, null)
+            val call = analyzeUrl.getResponse()
+            val response = call.execute()
+            if (response.body() != null) {
+                return response.body()!!.toString()
+            }
+        } catch (e: Exception) {
+            return e.localizedMessage
+        }
+
+        return null
+    }
+
+    /**
+     * js实现解码,不能删
+     */
+    fun base64Decoder(str: String): String {
+        return Encoder.base64Decoder(str)
+    }
+
+    /**
+     * 章节数转数字
+     */
+    fun toNumChapter(s: String?): String? {
+        if (s == null) {
+            return null
+        }
+        val pattern = Pattern.compile("(第)(.+?)(章)")
+        val matcher = pattern.matcher(s)
+        return if (matcher.find()) {
+            matcher.group(1) + StringUtils.stringToInt(matcher.group(2)) + matcher.group(3)
+        } else {
+            s
+        }
+    }
+
+}