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Supabase Backend as a Service · Lesson

Connecting Your App with the Supabase Client

Install the Supabase JavaScript client, initialize it with your project URL and anon key, and run your first request to confirm the connection.

Connecting Your App with the Supabase Client is a free Supabase Backend as a Service lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Supabase Backend as a Service learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

From Dashboard to Code

Dashboard done — now you talk to Supabase from code using its client library. For JavaScript and TypeScript, reach for supabase-js.

Installing the Client

Add the official supabase-js package to your project with your package manager.

npm install @supabase/supabase-js

Where to Find Your Keys

Under Project Settings > API you will find your Project URL, the browser-safe anon key, and the service_role key for servers only.

Creating the Client

Call createClient once with your URL and anon key, then reuse that single instance everywhere in your app.

import { createClient } from '@supabase/supabase-js';
const supabase = createClient(
  'https://your-project.supabase.co',
  'your-anon-key'
);

Keep Secrets in Env Vars

Never hardcode keys in committed code — read them from environment variables instead.

const url = process.env.SUPABASE_URL;
const key = process.env.SUPABASE_ANON_KEY;
console.log('Configured:', Boolean(url && key));

Your First Query

Run your first query with select. The client returns a data array and an error object, never throwing on its own.

const { data, error } = await supabase
  .from('todos')
  .select('*');
if (error) console.error(error.message);
else console.log(data);

Always Handle the Error

Supabase will not throw on a failed query, so check error every time before you touch data.

function handle(result) {
  if (result.error) return 'Failed: ' + result.error;
  return 'Got ' + result.data.length + ' rows';
}
console.log(handle({ data: [1, 2], error: null }));

Inserting Data

Write a row with insert, passing an array of objects. Add select to get the inserted rows back.

const { data, error } = await supabase
  .from('todos')
  .insert([{ title: 'Learn Supabase', done: false }])
  .select();

Client vs Server Keys

The anon key is guarded by Row-Level Security and safe in the browser. The service_role key bypasses RLS, so keep it server-only.

Confirming the Connection

Quick health check: select a single row. Real data or a clear permission error (not a network error) means your client is wired correctly.

Reusing One Instance

Export your configured client from one module and import it everywhere. A single instance avoids duplicate connections and config drift.

Quick Check

Test your understanding of connecting with the client.

Recap

Recap: you installed supabase-js, built a client from env vars, ran your first select and insert, and learned why anon keys are browser-safe.

Frequently asked questions

Is the “Connecting Your App with the Supabase Client” lesson free?

Yes — the full text of “Connecting Your App with the Supabase Client” is free to read here on the web, and the Supabase Backend as a Service course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Supabase Backend as a Service course, upgrade to CoddyKit PRO.

What will I learn in “Connecting Your App with the Supabase Client”?

Install the Supabase JavaScript client, initialize it with your project URL and anon key, and run your first request to confirm the connection. You practise Supabase Backend as a Service with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Supabase Backend as a Service?

No prior experience is required. Supabase Backend as a Service on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Connecting Your App with the Supabase Client” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Supabase Backend as a Service lesson?

Yes. Every Supabase Backend as a Service lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Introduction to BaaS & Supabase
  2. Setting Up Your First Project
  3. The Supabase Dashboard Tour
  4. Connecting Your App with the Supabase Client
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