Someone who's worked with the Fitbit API knows the answer to this question...

I'm using "npm fitbit-node" and I am poised on the threshold of great things!

Here's the "app.js" file and I've emboldened that section of the code that I've got a question about:

// initialize the express application
const express = require("express");
const app = express();

// initialize the Fitbit API client
const FitbitApiClient = require("fitbit-node");
const client = new FitbitApiClient({
	clientId: "CLIENT_ID", //client_id
	clientSecret: "CLIENT_SECRET", //client secret
	apiVersion: '1.2' // 1.2 is the default
});

// redirect the user to the Fitbit authorization page
app.get("/authorize", (req, res) => {
	// request access to the user's activity, heartrate, location, nutrion, profile, settings, sleep, social, and weight scopes
	res.redirect(client.getAuthorizeUrl('activity heartrate location nutrition profile settings sleep social weight', 'http://localhost:3000/callback')); //callback url
});

// handle the callback from the Fitbit authorization flow
app.get("/callback", (req, res) => {
	// exchange the authorization code we just received for an access token
	client.getAccessToken(req.query.code, 'http://localhost:3000/callback').then(result => { //callback url
		// use the access token to fetch the user's profile information
		[b]client.get("/profile.json", result.access_token)[/b]
		[u]//client.get ("/1/user/[user-id]/[resource-path]/date/[date]/[period].json", result.access_token)[/u]
		.then(results => {
			res.send(results[0]);
			console.log(results[0].user.age);
		}).catch(err => {
			res.status(err.status).send(err);
		});
	}).catch(err => {
		res.status(err.status).send(err);
	});
});

// launch the server
app.listen(3000);

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Smell that? That's the aroma of success! After I've gone through the process of logging in, I get my call back and it looks like this:

{ 
   "user":{ 
      "age":22,
      "ambassador":false,
      "autoStrideEnabled":true,
      "avatar":"https://static0.fitbit.com/images/profile/defaultProfile_100.png",
      "avatar150":"https://static0.fitbit.com/images/profile/defaultProfile_150.png",
      "avatar640":"https://static0.fitbit.com/images/profile/defaultProfile_640.png",
      "averageDailySteps":5296,
      "clockTimeDisplayFormat":"12hour",
      "corporate":false,
      "corporateAdmin":false,
      "dateOfBirth":"1983-08-26",
      "displayName":"Bruce G.",
      "displayNameSetting":"name",
      "distanceUnit":"en_US",
      "encodedId":"7V335V",
      "familyGuidanceEnabled":false,
      "features":{ 
         "exerciseGoal":true
      },
      "firstName":"Bruce",
      "foodsLocale":"en_US",
      "fullName":"Bruce Gust",
      "gender":"MALE",
      "glucoseUnit":"en_US",
      "height":175.20000000000002,
      "heightUnit":"en_US",
      "isChild":false,
      "isCoach":false,
      "lastName":"Gust",
      "locale":"en_US",
      "memberSince":"2019-10-22",
      "mfaEnabled":false,
      "offsetFromUTCMillis":-21600000,
      "startDayOfWeek":"SUNDAY",
      "strideLengthRunning":95.60000000000001,
      "strideLengthRunningType":"default",
      "strideLengthWalking":72.7,
      "strideLengthWalkingType":"default",
      "swimUnit":"en_US",
      "timezone":"America/Chicago",
      "topBadges":[ 
         { 
            "badgeGradientEndColor":"00D3D6",
            "badgeGradientStartColor":"007273",
            "badgeType":"DAILY_STEPS",
            "category":"Daily Steps",
            "cheers":[ 

            ],
            "dateTime":"2019-11-04",
            "description":"15,000 steps in a day",
            "earnedMessage":"Congrats on earning your first Urban Boot badge!",
            "encodedId":"228TMK",
            "image100px":"https://static0.fitbit.com/images/badges_new/100px/badge_daily_steps15k.png",
            "image125px":"https://static0.fitbit.com/images/badges_new/125px/badge_daily_steps15k.png",
            "image300px":"https://static0.fitbit.com/images/badges_new/300px/badge_daily_steps15k.png",
            "image50px":"https://static0.fitbit.com/images/badges_new/badge_daily_steps15k.png",
            "image75px":"https://static0.fitbit.com/images/badges_new/75px/badge_daily_steps15k.png",
            "marketingDescription":"You've walked 15,000 steps  And earned the Urban Boot badge!",
            "mobileDescription":"With a number that's almost three times more than the national average, your step count is really heating up.",
            "name":"Urban Boot (15,000 steps in a day)",
            "shareImage640px":"https://static0.fitbit.com/images/badges_new/386px/shareLocalized/en_US/badge_daily_steps15k.png",
            "shareText":"I took 15,000 steps and earned the Urban Boot badge! #Fitbit",
            "shortDescription":"15,000 steps",
            "shortName":"Urban Boot",
            "timesAchieved":1,
            "value":15000
         },
         { 
            "badgeGradientEndColor":"38D7FF",
            "badgeGradientStartColor":"2DB4D7",
            "badgeType":"DAILY_FLOORS",
            "category":"Daily Climb",
            "cheers":[ 

            ],
            "dateTime":"2019-11-04",
            "description":"50 floors in a day",
            "earnedMessage":"Congrats on earning your first Lighthouse badge!",
            "encodedId":"228TT7",
            "image100px":"https://static0.fitbit.com/images/badges_new/100px/badge_daily_floors50.png",
            "image125px":"https://static0.fitbit.com/images/badges_new/125px/badge_daily_floors50.png",
            "image300px":"https://static0.fitbit.com/images/badges_new/300px/badge_daily_floors50.png",
            "image50px":"https://static0.fitbit.com/images/badges_new/badge_daily_floors50.png",
            "image75px":"https://static0.fitbit.com/images/badges_new/75px/badge_daily_floors50.png",
            "marketingDescription":"You've climbed 50 floors to earn the Lighthouse badge!",
            "mobileDescription":"With a floor count this high, you're a beacon of inspiration to us all!",
            "name":"Lighthouse (50 floors in a day)",
            "shareImage640px":"https://static0.fitbit.com/images/badges_new/386px/shareLocalized/en_US/badge_daily_floors50.png",
            "shareText":"I climbed 50 flights of stairs and earned the Lighthouse badge! #Fitbit",
            "shortDescription":"50 floors",
            "shortName":"Lighthouse",
            "timesAchieved":1,
            "value":50
         }
      ],
      "waterUnit":"en_US",
      "waterUnitName":"fl oz",
      "weight":81.6,
      "weightUnit":"en_US"
   }
}

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Outstanding! But...

If I want heart beat or activity log, I'm stuck because all I've got here is profile info.

According to https://dev.fitbit.com/build/reference/web-api/user/, I can get everything that I need, but I need the "client-id..."

GET https://api.fitbit.com/1/user/[user-id]/profile.json

According to this site, the user-id is something I can access from the profile end point, but I don't see it anywhere in the json that gets returned when I ask specifically for "profile.json" (the json that I've got above).

So,, my question is: Where do I get the client-id from? Every URL that contains the info I need requires that piece of info and I'm thinking that someone who's worked with the Fitbit API probably knows exactly where I need to be looking.

Thoughts?