Node

Install the Latest Version

npm

npm install @prefab-cloud/prefab-cloud-node

yarn

yarn add @prefab-cloud/prefab-cloud-node

Initialize a Client

import { Prefab } from "@prefab-cloud/prefab-cloud-node";

if (!process.env.PREFAB_API_KEY) {
  throw new Error("PREFAB_API_KEY is not set");
}

const prefab = new Prefab({
  apiKey: process.env.PREFAB_API_KEY,
  enableSSE: true,
  defaultLogLevel: "warn",
});

await prefab.init();

Feature Flags and Dynamic Config

After the init completes you can use

• prefab.isFeatureEnabled('some.feature.name') returns true or false
• prefab.get('some.config.name') returns a raw value

Context

Prefab supports context for intelligent rule-based evaluation of get and isFeatureEnabled based on the current request/device/user/etc.

Given

const context = new Map([
  [
    "user",
    new Map([
      ["key", "some-unique-identifier"],
      ["country", "US"],
    ]),
  ],

  [
    "subscription",
    new Map([
      ["key", "pro-sub"],
      ["plan", "pro"],
    ]),
  ],
]);

You can pass this in to each call

• prefab.get('some.config.name', context, defaultValue)
• prefab.isFeatureEnabled('some.feature.name', context, false)

Or you can set the context in a block (perhaps surrounding evaluation of a web request)

prefab.inContext(context, (pf) => {
  const optionalJustInTimeContext = { ... }

  console.log(pf.get("some.config.name", optionalJustInTimeContext, defaultValue))
  console.log(pf.isEnabled("some.config.name", optionalJustInTimeContext, false))
})

Dynamic Logging

prefab.shouldLog(loggerName, desiredLevel, defaultLevel, contexts) returns true or false

Reference

Option Definitions

Name	Description	Default
collectEvaluationSummaries	Send counts of config/flag evaluation results back to Prefab to view in web app	true
collectLoggerCounts	Send counts of logger usage back to Prefab to power log-levels configuration screen	true
contextUploadMode	Upload either context "shapes" (the names and data types your app uses in prefab contexts) or periodically send full example contexts	"periodicExample"
defaultLevel	Level to be used as the min-verbosity for a loggerPath if no value is configured in Prefab	"warn"
enableSSE	Whether or not we should listen for live changes from Prefab	true
enablePolling	Whether or not we should poll for changes from Prefab	false