launchdarkly_node_server_sdk_feature_flag_evaluation_quickstart.ts

1import * as LaunchDarkly from '@launchdarkly/node-server-sdk';
2
3// Set sdkKey to your LaunchDarkly SDK key.
4const sdkKey: string = "your-sdk-key";
5
6// Set featureFlagKey to the key of the feature flag you want to evaluate.
7const featureFlagKey: string = "sample-feature-flag-key";
8
9// Set up the context properties. This context should appear on your LaunchDarkly contexts dashboard
10// after you run the SDK.
11const context: LaunchDarkly.LDContext = {
12  kind: 'user',
13  key: 'example-user-key',
14  name: 'Sandy'
15};
16
17const client = LaunchDarkly.init(sdkKey);
18
19async function main() {
20  try {
21    // Wait for the client to initialize
22    await client.waitForInitialization();
23    console.log("SDK successfully initialized!");
24
25    // Evaluate the feature flag
26    const flagValue = await client.variation(featureFlagKey, context, false);
27
28    console.log(`The condition for ${featureFlagKey} is ${flagValue}`);
29
30    if (flagValue) {
31      console.log("Showing feature for user");
32    } else {
33      console.log("Not showing feature for user");
34    }
35  } catch (err) {
36    console.error(`SDK failed to initialize: ${err}`);
37  } finally {
38    // Close the client to ensure all events are delivered to LaunchDarkly
39    client.close();
40  }
41}
42
43main();