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Node.js

Getting started

1. Install ConfigCat SDK

via NPM

npm i configcat-node

2. Import package

const configcat = require("configcat-node");

3. Create the ConfigCat client with your API Key

let configCatClient = configcat.createClient("#YOUR-API-KEY#");

4. Get your setting value

configCatClient.getValue("isMyAwesomeFeatureEnabled", false, (value) => {
    if(value) {
        do_the_new_thing();
    } else {
        do_the_old_thing();
    }
});

Creating the ConfigCat Client

ConfigCat Client is responsible for:

  • managing the communication between your application and ConfigCat servers.
  • caching your setting values and feature flags.
  • serving values quickly in a failsafe way.

createClient() returns a client with default options.

PropertiesDescription
apiKeyREQUIRED. API Key to access your feature flags and configurations. Get it from ConfigCat Management Console.

createClientWithAutoPoll(), createClientWithLazyLoad(), createClientWithManualPoll()
Creating the client is different for each polling mode. See below for details.

We strongly recommend using the ConfigCat Client as a Singleton object in your application.

Anatomy of getValue()

ParametersDescription
keyREQUIRED. Setting-specific key. Set in ConfigCat Management Console for each setting.
defaultValueREQUIRED. This value will be returned in case of an error.
callbackREQUIRED. Called with the actual setting value.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
 
configCatClient.getValue(
    "keyOfMySetting", // Setting Key
    false, // Default value
    (value) => { console.log(value) }, // Callback function
    { identifier : "435170f4-8a8b-4b67-a723-505ac7cdea92" } // Optional User Object
);

User Object

let userObject = {
    identifier : "435170f4-8a8b-4b67-a723-505ac7cdea92"
};   

let userObject = {
    identifier : "john@example.com"
};
ParametersDescription
identifierREQUIRED. Unique identifier of a user in your application. Can be any string value, even an email address.
emailOptional parameter for easier targeting rule definitions.
countryOptional parameter for easier targeting rule definitions.
customOptional dictionary for custom attributes of a user for advanced targeting rule definitions. e.g. User role, Subscription type.
 
let userObject = {
    identifier : "435170f4-8a8b-4b67-a723-505ac7cdea92",
    email : "john@example.com",
    country : "United Kingdom",
    custom : {
        "SubscriptionType": "Pro",
        "UserRole": "Admin"
    }
};

Polling Modes

The ConfigCat SDK supports 3 different polling mechanisms to acquire the setting values from ConfigCat. After latest setting values are downloaded, they are stored in the internal cache then all requests are served from there. With the following polling modes, you can customize the SDK to best fit to your application's lifecycle.

Auto polling (default)

The ConfigCat SDK downloads the latest values and stores them automatically every 60 seconds.

Use the pollIntervalSeconds option parameter to change the polling interval.

let configCatClient = configcat.createClientWithAutoPoll("#YOUR-API-KEY#", { pollIntervalSeconds: 95 });

Adding a callback to configChanged option parameter will get you notified about changes.

let configCatClient = configcat.createClientWithAutoPoll("#YOUR-API-KEY#", { configChanged: () => {
    console.log("Your config has been changed!");
}});

Available options:

Option ParameterDescriptionDefault
pollIntervalSecondsPolling interval. Range: 1 - Number.MAX_SAFE_INTEGER60
configChangedCallback to get notified about changes.-
loggerCustom logger. See below for details.Console logger

Lazy loading

When calling getValue() the ConfigCat SDK downloads the latest setting values if they are not present or expired in the cache. In this case the callback will be called after the cache is updated.

Use cacheTimeToLiveSeconds option parameter to set cache lifetime.

let configCatClient = configcat.createClientWithLazyLoad("#YOUR-API-KEY#", { cacheTimeToLiveSeconds: 600 });

Available options:

Option ParameterDescriptionDefault
cacheTimeToLiveSecondsCache TTL. Range: 1 - Number.MAX_SAFE_INTEGER60
loggerCustom logger. See below for details.Console logger

Manual polling

Manual polling gives you full control over when the setting values are downloaded. ConfigCat SDK will not update them automatically. Calling forceRefresh() is your application's responsibility.

let configCatClient = configcat.createClientWithManualPoll("#YOUR-API-KEY#");

configCatClient.forceRefresh(() =>{

    configCatClient.getValue("key", "my default value", (value)=>{
        
        console.log(value);
    });
});

Available options:

Option ParameterDescriptionDefault
loggerCustom logger. See below for details.Console logger

getValue() returns defaultValue if the cache is empty. Call forceRefresh() to update the cache.

let configCatClient = configcat.createClientWithManualPoll("#YOUR-API-KEY#");

configCatClient.getValue("key", "my default value", (value)=>{

    console.log(value) // console: "my default value"
});

configCatClient.forceRefresh(() =>{

    configCatClient.getValue("key", "my default value", (value)=>{

        console.log(value); // console: "value from server"
    });
});

Logging

To customize logging create a logger instance and add it to Options object when creating the ConfigCat client. 2 log levels are supported: log and error.

let customLogger = {
    log: (message) => {
        console.log('ConfigCat log: ' + message);
    },
    error: (message) => {
        console.error('ConfigCat log: ' + message);
    }
};

let configCatClient = configcat.createClientWithManualPoll("#YOUR-API-KEY#", { logger: customLogger });

CDN base url (forward proxy, dedicated subscription)

You can customize your CDN path in the SDK with baseUrl property in the options parameter.

let configCatClient = configcat.createClientWithManualPoll("#YOUR-API-KEY#", { baseUrl: "https://myCDN.configcat.com" });

getAllKeys()

You can query the keys from your config file in the SDK with the getAllKeys() method.

let configCatClient = configcat.createClient("#YOUR-API-KEY#");
configCatClient.getAllKeys((keys)=>{
    console.log(keys);
});

Sample Application

Sample Console App

Look under the hood

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