TAS Client UMD Module

Common errors

• TypeError: TASClient is not a constructor

  cause Attempting to use `const TASClient = require('tas-client-umd'); new TASClient()` in CommonJS, instead of destructuring the import.
  fix In CommonJS, use `const { TASClient } = require('tas-client-umd');` or access via the default export if bundling: `const TASClient = require('tas-client-umd').TASClient;`

• ReferenceError: TASClient is not defined

  cause In a browser environment using the UMD build, the global variable might not be accessible, or the script tag for `tas-client-umd` was not loaded before its usage.
  fix Ensure the `tas-client-umd` script is loaded in your HTML before any code attempts to use `TASClient`. Verify the global variable name exposed by the UMD bundle.

• Property 'isFlightEnabled' is deprecated.

  cause Using the `isFlightEnabled` method which has been marked for removal.
  fix Update your code to use `getTreatmentVariable(configId, name)` instead of `isFlightEnabled(flightName)`.

Warnings

• deprecated The `isFlightEnabled` method on `IExperimentationService` is deprecated. Consumers should transition to using `getTreatmentVariable` instead for retrieving experiment values.
  Fix: Replace calls to `tasClient.isFlightEnabled(flightName)` with `tasClient.getTreatmentVariable(configId, variableName)`.
• gotcha The `TASClient` requires multiple interfaces (`IExperimentationFilterProvider`, `IExperimentationTelemetry`, `IKeyValueStorage`) to be implemented by the consumer and provided during construction. Failing to do so or providing incomplete implementations will lead to runtime errors.
  Fix: Ensure all required interfaces are fully implemented with the necessary methods before instantiating `TASClient`. Refer to the interface definitions for details.
• gotcha Calling `tasClient.getTreatmentVariable()` before the experimentation service has fully initialized (i.e., before `tasClient.initializePromise` resolves) will result in a runtime error. If you cannot await initialization, use `getTreatmentVariableAsync()`.
  Fix: Always await `tasClient.initializePromise` before making synchronous calls to `getTreatmentVariable()`. If an asynchronous API is required before full initialization, use the `getTreatmentVariableAsync()` method.

Install

• npm install tas-client-umd npm
• yarn add tas-client-umd yarn
• pnpm add tas-client-umd pnpm

Imports

• TASClient
  wrong:

  const TASClient = require('tas-client-umd');

  correct:

  import { TASClient } from 'tas-client-umd';

  For CommonJS, use destructuring: `const { TASClient } = require('tas-client-umd');`. Direct `require()` without destructuring will yield an object containing the exports.
• IExperimentationService
  wrong:

  import IExperimentationService from 'tas-client-umd';

  correct:

  import { IExperimentationService } from 'tas-client-umd';

  All interfaces are named exports. This package ships TypeScript types.
• IKeyValueStorage

  import type { IKeyValueStorage } from 'tas-client-umd';

  Type-only import for interfaces when not used as a value, for bundler tree-shaking and type safety.

Quickstart

This quickstart demonstrates how to instantiate `TASClient` with mock interface implementations and retrieve a treatment variable after initialization.

import { TASClient } from 'tas-client-umd';

// Mock implementations for required interfaces
const mockFilterProvider = {
    getFilters: () => new Map([['region', 'us'], ['platform', 'web']])
};

const mockTelemetry = {
    setSharedProperty: (name, value) => console.log(`Telemetry shared property: ${name}=${value}`),
    postEvent: (eventName, props) => console.log(`Telemetry event: ${eventName}, props: ${JSON.stringify(Object.fromEntries(props))}`)
};

const mockKeyValueStorage = {
    _storage: new Map(),
    getValue: async (key, defaultValue) => {
        const value = mockKeyValueStorage._storage.get(key);
        return value !== undefined ? value : defaultValue;
    },
    setValue: (key, value) => {
        mockKeyValueStorage._storage.set(key, value);
    }
};

const tasClient = new TASClient({
    filterProviders: [mockFilterProvider],
    telemetry: mockTelemetry,
    storageKey: 'my-tas-experiments',
    keyValueStorage: mockKeyValueStorage,
    assignmentContextTelemetryPropertyName: 'myExpContext',
    telemetryEventName: 'MyExperimentationQuery',
    endpoint: process.env.TAS_ENDPOINT ?? 'https://example.com/tas-api', // Replace with your actual endpoint
    refetchInterval: 30000 // Refetch every 30 seconds
});

// Initialize the client and fetch a treatment variable
tasClient.initializePromise.then(async () => {
    console.log('TASClient initialized successfully.');
    // Example: Getting a treatment variable
    const treatmentValue = await tasClient.getTreatmentVariable('my-feature-config', 'my-variable-name');
    console.log(`Treatment variable 'my-variable-name': ${treatmentValue}`);
}).catch(error => {
    console.error('Failed to initialize TASClient:', error);
});