diff --git a/cli/js/tests/url_search_params_test.ts b/cli/js/tests/url_search_params_test.ts
index 3e71d29003..7b7dbab764 100644
--- a/cli/js/tests/url_search_params_test.ts
+++ b/cli/js/tests/url_search_params_test.ts
@@ -243,3 +243,33 @@ unitTest(
     assertEquals(params1.get("1"), "2");
   }
 );
+
+// If a class extends URLSearchParams, override one method should not change another's behavior.
+unitTest(
+  function urlSearchParamsOverridingAppendNotChangeConstructorAndSet(): void {
+    let overridedAppendCalled = 0;
+    class CustomSearchParams extends URLSearchParams {
+      append(name: string, value: string): void {
+        ++overridedAppendCalled;
+        super.append(name, value);
+      }
+    }
+    new CustomSearchParams("foo=bar");
+    new CustomSearchParams([["foo", "bar"]]);
+    new CustomSearchParams(new CustomSearchParams({ foo: "bar" }));
+    new CustomSearchParams().set("foo", "bar");
+    assertEquals(overridedAppendCalled, 0);
+  }
+);
+
+unitTest(function urlSearchParamsOverridingEntriesNotChangeForEach(): void {
+  class CustomSearchParams extends URLSearchParams {
+    *entries(): IterableIterator<[string, string]> {
+      yield* [];
+    }
+  }
+  let loopCount = 0;
+  const params = new CustomSearchParams({ foo: "bar" });
+  params.forEach(() => void ++loopCount);
+  assertEquals(loopCount, 1);
+});
diff --git a/cli/js/web/url_search_params.ts b/cli/js/web/url_search_params.ts
index 221a70ab12..35439b0e2e 100644
--- a/cli/js/web/url_search_params.ts
+++ b/cli/js/web/url_search_params.ts
@@ -5,56 +5,17 @@ import { isIterable, requiredArguments } from "./util.ts";
 /** @internal */
 export const urls = new WeakMap<URLSearchParams, URL | null>();
 
-function handleStringInitialization(
-  searchParams: URLSearchParams,
-  init: string
-): void {
-  // Overload: USVString
-  // If init is a string and starts with U+003F (?),
-  // remove the first code point from init.
-  if (init.charCodeAt(0) === 0x003f) {
-    init = init.slice(1);
-  }
-
-  for (const pair of init.split("&")) {
-    // Empty params are ignored
-    if (pair.length === 0) {
-      continue;
-    }
-    const position = pair.indexOf("=");
-    const name = pair.slice(0, position === -1 ? pair.length : position);
-    const value = pair.slice(name.length + 1);
-    searchParams.append(decodeURIComponent(name), decodeURIComponent(value));
-  }
-}
-
-function handleArrayInitialization(
-  searchParams: URLSearchParams,
-  init: string[][] | Iterable<[string, string]>
-): void {
-  // Overload: sequence<sequence<USVString>>
-  for (const tuple of init) {
-    // If pair does not contain exactly two items, then throw a TypeError.
-    if (tuple.length !== 2) {
-      throw new TypeError(
-        "URLSearchParams.constructor tuple array argument must only contain pair elements"
-      );
-    }
-    searchParams.append(tuple[0], tuple[1]);
-  }
-}
-
 export class URLSearchParamsImpl implements URLSearchParams {
   #params: Array<[string, string]> = [];
 
   constructor(init: string | string[][] | Record<string, string> = "") {
     if (typeof init === "string") {
-      handleStringInitialization(this, init);
+      this.#handleStringInitialization(init);
       return;
     }
 
     if (Array.isArray(init) || isIterable(init)) {
-      handleArrayInitialization(this, init);
+      this.#handleArrayInitialization(init);
       return;
     }
 
@@ -69,12 +30,47 @@ export class URLSearchParamsImpl implements URLSearchParams {
 
     // Overload: record<USVString, USVString>
     for (const key of Object.keys(init)) {
-      this.append(key, init[key]);
+      this.#append(key, init[key]);
     }
 
     urls.set(this, null);
   }
 
+  #handleStringInitialization = (init: string): void => {
+    // Overload: USVString
+    // If init is a string and starts with U+003F (?),
+    // remove the first code point from init.
+    if (init.charCodeAt(0) === 0x003f) {
+      init = init.slice(1);
+    }
+
+    for (const pair of init.split("&")) {
+      // Empty params are ignored
+      if (pair.length === 0) {
+        continue;
+      }
+      const position = pair.indexOf("=");
+      const name = pair.slice(0, position === -1 ? pair.length : position);
+      const value = pair.slice(name.length + 1);
+      this.#append(decodeURIComponent(name), decodeURIComponent(value));
+    }
+  };
+
+  #handleArrayInitialization = (
+    init: string[][] | Iterable<[string, string]>
+  ): void => {
+    // Overload: sequence<sequence<USVString>>
+    for (const tuple of init) {
+      // If pair does not contain exactly two items, then throw a TypeError.
+      if (tuple.length !== 2) {
+        throw new TypeError(
+          "URLSearchParams.constructor tuple array argument must only contain pair elements"
+        );
+      }
+      this.#append(tuple[0], tuple[1]);
+    }
+  };
+
   #updateSteps = (): void => {
     const url = urls.get(this);
     if (url == null) {
@@ -89,9 +85,13 @@ export class URLSearchParamsImpl implements URLSearchParams {
     parts.get(url)!.query = query;
   };
 
+  #append = (name: string, value: string): void => {
+    this.#params.push([String(name), String(value)]);
+  };
+
   append(name: string, value: string): void {
     requiredArguments("URLSearchParams.append", arguments.length, 2);
-    this.#params.push([String(name), String(value)]);
+    this.#append(name, value);
     this.#updateSteps();
   }
 
@@ -167,7 +167,7 @@ export class URLSearchParamsImpl implements URLSearchParams {
     // Otherwise, append a new name-value pair whose name is name
     // and value is value, to list.
     if (!found) {
-      this.append(name, value);
+      this.#append(name, value);
     }
 
     this.#updateSteps();
@@ -189,7 +189,7 @@ export class URLSearchParamsImpl implements URLSearchParams {
       callbackfn = callbackfn.bind(thisArg);
     }
 
-    for (const [key, value] of this.entries()) {
+    for (const [key, value] of this.#params) {
       callbackfn(value, key, this);
     }
   }