@quonfig/javascript

Feature flags and dynamic configuration for the browser. The client fetches an evaluated config snapshot over HTTP and keeps it fresh by polling, so flag evaluation is a local, synchronous read.

Install

npm install @quonfig/javascript

Usage

import { quonfig } from "@quonfig/javascript";

await quonfig.init({
  sdkKey: "your-frontend-sdk-key",
  context: { user: { key: "user-123" } },
});

if (quonfig.isEnabled("my-flag")) {
  // ...
}

const color = quonfig.get("button-color");

Failover & QUONFIG_DOMAIN

By default the SDK derives its URLs from a single domain (default quonfig.com) and ships a primary and a secondary config-fetch leg:

Role                     URL
------------------------ ---------------------------------
Config fetch (primary)   https://primary.quonfig.com
Config fetch (secondary) https://secondary.quonfig.com
Telemetry                https://telemetry.quonfig.com

(This SDK polls HTTP for config; it does not open an SSE stream, so there are no stream.* URLs.)

Point all of them at a different environment with the domain init option — the documented browser knob, which flips the config and telemetry URLs in lockstep:

await quonfig.init({
  sdkKey: "your-frontend-sdk-key",
  context: { user: { key: "user-123" } },
  domain: "quonfig-staging.com",
});

QUONFIG_DOMAIN is also honored, but only where process.env exists — Node-side, SSR, or when a bundler inlines it at build time. A pure browser runtime has no process.env, so prefer the domain option there. Resolution order (highest wins): explicit apiUrls > domain option > process.env.QUONFIG_DOMAIN > "quonfig.com".

Automatic failover is on by default. The secondary runs on separate infrastructure; the SDK hedges to it if the primary is slow and fails over to it if the primary is unreachable.

apiUrls replaces the derived list wholesale. To keep automatic failover with custom URLs, pass both a primary and a secondary URL:

await quonfig.init({
  sdkKey: "your-frontend-sdk-key",
  context: { user: { key: "user-123" } },
  apiUrls: ["https://primary.your-proxy.example", "https://secondary.your-proxy.example"],
});

A single-URL apiUrls (or the singular apiUrl) drops the secondary and disables failover, and the SDK logs a warning at init.

See https://docs.quonfig.com/docs/explanations/architecture/resiliency for the full model.