feat: added persisted Switchers for better resource utilization #215

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Merged

petruki merged 2 commits into master from staging

Jan 8, 2026

README.md

            
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    @@ -1,7 +1,7 @@
  
    ***

    <div align="center">

    <b>Switcher Client SDK</b><br>

    <b>Switcher Client JS SDK</b><br>

    A JavaScript SDK for Switcher API

    </div>

    @@ -81,10 +81,10 @@ Client.buildContext({
  
    });

    // 2. Get a switcher instance

    const switcher = Client.getSwitcher();

    const switcher = Client.getSwitcher('FEATURE01');

    // 3. Check if a feature is enabled

    const isFeatureEnabled = await switcher.isItOn('FEATURE01');

    const isFeatureEnabled = await switcher.isItOn();

    console.log('Feature enabled:', isFeatureEnabled);

    ```

    @@ -177,19 +177,22 @@ Client.buildContext({
  
    Multiple ways to check if a feature is enabled:

    ```js

    // Non-persisted switcher instance

    const switcher = Client.getSwitcher();

    // Persisted switcher instance

    const switcher = Client.getSwitcher('FEATURE01');

    // 🚀 Synchronous (local mode only)

    const isEnabled = switcher.isItOn('FEATURE01');              // Returns: boolean

    const isEnabledBool = switcher.isItOnBool('FEATURE01');      // Returns: boolean

    const detailResult = switcher.detail().isItOn('FEATURE01');  // Returns: { result, reason, metadata }

    const detailDirect = switcher.isItOnDetail('FEATURE01');     // Returns: { result, reason, metadata }

    const isEnabled = switcher.isItOn();              // Returns: boolean

    const isEnabledBool = switcher.isItOnBool();      // Returns: boolean

    const detailResult = switcher.detail().isItOn();  // Returns: { result, reason, metadata }

    const detailDirect = switcher.isItOnDetail();     // Returns: { result, reason, metadata }

    // 🌐 Asynchronous (remote/hybrid mode)

    const isEnabledAsync = await switcher.isItOn('FEATURE01');              // Returns: Promise<boolean>

    const isEnabledBoolAsync = await switcher.isItOnBool('FEATURE01', true); // Returns: Promise<boolean>

    const detailResultAsync = await switcher.detail().isItOn('FEATURE01');  // Returns: Promise<SwitcherResult>

    const detailDirectAsync = await switcher.isItOnDetail('FEATURE01', true); // Returns: Promise<SwitcherResult>

    const isEnabledAsync = await switcher.isItOn();               // Returns: Promise<boolean>

    const isEnabledBoolAsync = await switcher.isItOnBool(true);   // Returns: Promise<boolean>

    const detailResultAsync = await switcher.detail().isItOn();   // Returns: Promise<SwitcherResult>

    const detailDirectAsync = await switcher.isItOnDetail(true);  // Returns: Promise<SwitcherResult>

    ```

    ### Strategy Validation

package.json

            
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    @@ -32,8 +32,8 @@
  
      ],

      "devDependencies": {

        "@babel/eslint-parser": "^7.28.5",

        "@typescript-eslint/eslint-plugin": "^8.50.1",

        "@typescript-eslint/parser": "^8.50.1",

        "@typescript-eslint/eslint-plugin": "^8.52.0",

        "@typescript-eslint/parser": "^8.52.0",

        "c8": "^10.1.3",

        "chai": "^6.2.2",

        "env-cmd": "^11.0.0",

src/client.d.ts

-Original file line number
+Diff line change
@@ Expand Up / @@ -16,7 +16,9 @@ export class Client { @@
       static buildContext(context: SwitcherContext, options?: SwitcherOptions): void;
       /**
-       * Creates a new instance of Switcher
+       * Creates a new instance of Switcher.
+       *
+       * Provide a key if you want to persist the instance.
        */
       static getSwitcher(key?: string): Switcher;
@@ Expand Down @@

src/client.js

-Original file line number
+Diff line change
@@ Expand Up / @@ -26,6 +26,7 @@ import { SnapshotWatcher } from './lib/snapshotWatcher.js'; @@
     export class Client {
       static #snapshotWatcher = new SnapshotWatcher();
+      static #switchers = new Map();
       static #testEnabled;
       static #context;
@@ Expand Down Expand Up / @@ -103,8 +104,21 @@ export class Client { @@
       }
       static getSwitcher(key) {
-        return new Switcher(util.get(key, ''))
+        const keyValue = util.get(key, '');
+        const persistedSwitcher = this.#switchers.get(keyValue);
+        if (persistedSwitcher) {
+          return persistedSwitcher;
+        }
+        const switcher = new Switcher(keyValue)
           .restrictRelay(GlobalOptions.restrictRelay);
+        if (keyValue) {
+          this.#switchers.set(keyValue, switcher);
+        }
+        return switcher;
       }
       static async checkSnapshot() {
@@ Expand Down @@

src/switcher.d.ts

            
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    @@ -16,65 +16,75 @@ export type SwitcherExecutionResult = Promise<boolean | SwitcherResult> | boolea
  
     * const { result, reason, metadata } = switcher.isItOnDetail();

     *

     * // Force asynchronous execution

     * const isOnAsync = await switcher.isItOnBool('MY_SWITCHER', true);

     * const detailAsync = await switcher.isItOnDetail('MY_SWITCHER', true);

     * const isOnAsync = await switcher.isItOnBool(true);

     * const detailAsync = await switcher.isItOnDetail(true);

     * ```

     */

    export class Switcher {

      /**

       * Execute criteria with boolean result (synchronous version)

       * Execute criteria with boolean result (synchronous, uses persisted key)

       *

       * @param key - switcher key

       * @param forceAsync - when true, forces async execution

       * @returns boolean value

       * @returns boolean result

       */

      isItOnBool(key: string, forceAsync?: false): boolean;

      isItOnBool(): boolean;

      /**

       * Execute criteria with boolean result (asynchronous version)

       * Execute criteria with boolean result (synchronous)

       *

       * @param key - switcher key

       * @returns boolean result

       */

      isItOnBool(key: string): boolean;

      /**

       * Execute criteria with boolean result (asynchronous, uses persisted key)

       *

       * @param forceAsync - when true, forces async execution

       * @returns Promise<boolean> value

       * @returns Promise<boolean> result

       */

      isItOnBool(key: string, forceAsync?: true): Promise<boolean>;

      isItOnBool(forceAsync: true): Promise<boolean>;

      /**

       * Execute criteria with boolean result

       * Execute criteria with boolean result (asynchronous)

       *

       * @param key - switcher key

       * @param forceAsync - when true, forces async execution

       * @returns boolean value or Promise<boolean> based on execution mode

       * @returns Promise<boolean> result

       */

      isItOnBool(key: string, forceAsync?: boolean): Promise<boolean> | boolean;

      isItOnBool(key: string, forceAsync: true): Promise<boolean>;

      /**

       * Execute criteria with detail information (synchronous version)

       * Execute criteria with detail information (synchronous)

       *

       * @param key - switcher key

       * @param forceAsync - when true, forces async execution

       * @returns SwitcherResult object

       */

      isItOnDetail(key: string, forceAsync?: false): SwitcherResult;

      isItOnDetail(): SwitcherResult;

      /**

       * Execute criteria with detail information (asynchronous version)

       * Execute criteria with detail information (synchronous)

       *

       * @param key - switcher key

       * @returns SwitcherResult object

       */

      isItOnDetail(key: string): SwitcherResult;

      /**

       * Execute criteria with detail information (asynchronous, uses persisted key)

       *

       * @param forceAsync - when true, forces async execution

       * @returns Promise<SwitcherResult> object

       */

      isItOnDetail(key: string, forceAsync?: true): Promise<SwitcherResult>;

      isItOnDetail(forceAsync: true): Promise<SwitcherResult>;

      /**

       * Execute criteria with detail information

       * Execute criteria with detail information (asynchronous)

       *

       * @param key - switcher key

       * @param forceAsync - when true, forces async execution

       * @returns SwitcherResult or Promise<SwitcherResult> based on execution mode

       * @returns Promise<SwitcherResult> object

       */

      isItOnDetail(key: string, forceAsync?: boolean): Promise<SwitcherResult> | SwitcherResult;

      isItOnDetail(key: string, forceAsync: true): Promise<SwitcherResult>;

      /**

       * Execute criteria

src/switcher.js

            
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    @@ -43,24 +43,36 @@ export class Switcher extends SwitcherRequest {
  
        }

      }

      isItOnBool(key, forceAsync = false) {

      isItOnBool(arg1, arg2) {

        this.detail(false);

        if (forceAsync) {

          return Promise.resolve(this.isItOn(key));

        // Handle case where first argument is forceAsync boolean

        if (typeof arg1 === 'boolean') {

          arg2 = arg1;

          arg1 = undefined;

        }

        return this.isItOn(key);

        if (arg2) {

          return Promise.resolve(this.isItOn(arg1));

        }

        return this.isItOn(arg1);

      }

      isItOnDetail(key, forceAsync = false) {

      isItOnDetail(arg1, arg2) {

        this.detail(true);

        if (forceAsync) {

          return Promise.resolve(this.isItOn(key));

        // Handle case where first argument is forceAsync boolean

        if (typeof arg1 === 'boolean') {

          arg2 = arg1;

          arg1 = undefined;

        }

        if (arg2) {

          return Promise.resolve(this.isItOn(arg1));

        }

        return this.isItOn(key);

        return this.isItOn(arg1);

      }

      isItOn(key) {

tests/playground/index.js

            
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    @@ -20,7 +20,7 @@ async function setupSwitcher(local) {
  
    }

    /**

     * This code snippet is a minimal example of how to configure and use Switcher4Deno locally.

     * This code snippet is a minimal example of how to configure and use switcher-client-js locally.

     * No remote API account is required.

     * 

     * Snapshot is loaded from file at tests/playground/snapshot/local.json

    @@ -57,11 +57,11 @@ const _testSimpleAPICall = async (local) => {
  
            .then(() => console.log('Switcher checked'))

            .catch(error => console.log(error));

        const switcher = Client.getSwitcher();

        const switcher = Client.getSwitcher(SWITCHER_KEY);

        setInterval(async () => {

            const time = Date.now();

            const result = await switcher.detail().isItOn(SWITCHER_KEY);

            const result = await switcher.detail().isItOn();

            console.log(`- ${Date.now() - time} ms - ${JSON.stringify(result)}`);

        }, 1000);

    };

    @@ -73,14 +73,15 @@ const _testThrottledAPICall = async () => {
  
        await Client.checkSwitchers([SWITCHER_KEY]);

        Client.subscribeNotifyError((error) => console.log(error));

        const switcher = Client.getSwitcher();

        switcher.throttle(1000);

        setInterval(async () => {

            const time = Date.now();

            const switcher = Client.getSwitcher(SWITCHER_KEY);

            switcher.throttle(5000);

            const result = await switcher

                .detail()

                .isItOn(SWITCHER_KEY);

                .isItOn();

            console.log(`- ${Date.now() - time} ms - ${JSON.stringify(result)}`);

        }, 1000);

    @@ -94,31 +95,32 @@ const _testSnapshotUpdate = async () => {
  
        console.log('checkSnapshot:', await Client.checkSnapshot());

    };

    // Requires remote API

    const _testAsyncCall = async () => {

        setupSwitcher(true);

        const switcher = Client.getSwitcher();

        setupSwitcher(false);

        const switcher = Client.getSwitcher(SWITCHER_KEY);

        console.log('Sync:', await switcher.isItOn(SWITCHER_KEY));

        console.log('Sync:', await switcher.isItOn());

        switcher.isItOn(SWITCHER_KEY)

        switcher.isItOn()

            .then(res => console.log('Promise result:', res))

            .catch(error => console.log(error));

    };

    // Does not require remote API

    const _testBypasser = async () => {

        setupSwitcher(true);

        const switcher = Client.getSwitcher();

        const switcher = Client.getSwitcher(SWITCHER_KEY);

        let result = await switcher.isItOn(SWITCHER_KEY);

        let result = await switcher.isItOn();

        console.log(result);

        Client.assume(SWITCHER_KEY).true();

        result = await switcher.isItOn(SWITCHER_KEY);

        result = await switcher.isItOn();

        console.log(result);

        Client.forget(SWITCHER_KEY);

        result = await switcher.isItOn(SWITCHER_KEY);

        result = await switcher.isItOn();

        console.log(result);

        Client.unloadSnapshot();

    @@ -158,13 +160,13 @@ const _testWatchSnapshotContextOptions = async () => {
  
        await Client.loadSnapshot();

        const switcher = Client.getSwitcher();

        const switcher = Client.getSwitcher(SWITCHER_KEY);

        setInterval(async () => {

            const time = Date.now();

            const result = await switcher

                .detail()

                .isItOn(SWITCHER_KEY);

                .isItOn();

            console.log(`- ${Date.now() - time} ms - ${JSON.stringify(result)}`);

        }, 1000);

    @@ -176,7 +178,7 @@ const _testSnapshotAutoUpdate = async () => {
  
            { local: true, logger: true });

        await Client.loadSnapshot({ watchSnapshot: false, fetchRemote: true });

        const switcher = Client.getSwitcher();

        const switcher = Client.getSwitcher(SWITCHER_KEY);

        Client.scheduleSnapshotAutoUpdate(1, {

            success: (updated) => console.log('In-memory snapshot updated', updated),

    @@ -185,7 +187,7 @@ const _testSnapshotAutoUpdate = async () => {
  
        setInterval(async () => {

            const time = Date.now();

            await switcher.checkValue('user_1').isItOn(SWITCHER_KEY);

            await switcher.checkValue('user_1').isItOn();

            console.clear();

            console.log(JSON.stringify(Client.getLogger(SWITCHER_KEY)), `executed in ${Date.now() - time}ms`);

        }, 2000);

tests/switcher-client.test.js

-Original file line number
+Diff line change
@@ Expand Up / @@ -48,13 +48,14 @@ describe('E2E test - Client local #1:', function () { @@
         await switcher
           .checkValue('Japan')
           .checkNetwork('10.0.0.3')
-          .prepare();
+          .prepare('FF2FOR2020');
-        assert.isTrue(await switcher.isItOn('FF2FOR2020') === true);
-        assert.isTrue(switcher.isItOnBool('FF2FOR2020') === true);
-        assert.isTrue(await switcher.isItOnBool('FF2FOR2020', true) === true);
-        assert.isTrue(switcher.isItOnDetail('FF2FOR2020').result === true);
-        assert.isTrue((await switcher.isItOnDetail('FF2FOR2020', true)).result === true);
+        assert.isTrue(switcher.isItOn() === true);
+        assert.isTrue(await switcher.isItOn() === true);
+        assert.isTrue(switcher.isItOnBool() === true);
+        assert.isTrue(await switcher.isItOnBool(true) === true);
+        assert.isTrue(switcher.isItOnDetail().result === true);
+        assert.isTrue((await switcher.isItOnDetail(true)).result === true);
       });
       it('should get execution from logger', async function () {
@@ Expand Down @@

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