Invoking Edge Functions from client in Supabase - Mini Project: Build & Apply

Invoking Edge Functions from client

📖 Scenario: You are building a web app that needs to call a serverless function hosted on Supabase Edge Functions. This function will return a greeting message based on the user's name.

🎯 Goal: Learn how to set up a client call to a Supabase Edge Function and handle the response.

📋 What You'll Learn

Create a variable to hold the user's name

Create a Supabase client instance with the correct URL and anon key

Call the Edge Function named 'hello' with the user's name as a parameter

Handle the response and store the greeting message

💡 Why This Matters

🌍 Real World

Calling serverless functions from client apps is common for adding dynamic, secure backend logic without managing servers.

💼 Career

Understanding how to invoke cloud functions from clients is essential for modern web developers and cloud engineers working with serverless architectures.

1

Create a variable for the user's name

Create a variable called userName and set it to the string 'Alice'.

Supabase

# Your code here

Hint

Use const to declare the variable and assign the exact string 'Alice'.

2

Create a Supabase client instance

Create a constant called supabase and assign it the result of calling createClient with the URL 'https://xyzcompany.supabase.co' and anon key 'public-anon-key'.

Supabase

const userName = 'Alice';
// Your code here

Hint

Use createClient from @supabase/supabase-js with the exact URL and anon key.

3

Call the Edge Function with the user's name

Use await supabase.functions.invoke to call the Edge Function named 'hello' with options { body: { name: userName } }. Destructure the result as const { data: response }.

Supabase

import { createClient } from '@supabase/supabase-js';

const userName = 'Alice';
const supabase = createClient('https://xyzcompany.supabase.co', 'public-anon-key');

// Your code here

Hint

Use await, destructure { data: response } from the invoke call, and pass { body: { name: userName } } as options.

4

Extract and store the greeting message

Create a constant called greeting and assign it the text content of response by calling await response.text().

Supabase

import { createClient } from '@supabase/supabase-js';

const userName = 'Alice';
const supabase = createClient('https://xyzcompany.supabase.co', 'public-anon-key');

const { data: response } = await supabase.functions.invoke('hello', {
  body: { name: userName }
});

// Your code here

Hint

Use await response.text() to get the message string.

Practice

1. What is the main purpose of using supabase.functions.invoke() in a client application?

easy

A. To create new user accounts automatically

B. To directly access the database without authentication

C. To upload files to Supabase storage

D. To call Edge Functions and get fast responses near the user

Solution

1. Step 1: Understand what Edge Functions do

   Edge Functions run code close to users to reduce delay and improve speed.

2. Step 2: Identify the role of supabase.functions.invoke()

   This method is used to call those Edge Functions from the client side.

3. Final Answer:

   To call Edge Functions and get fast responses near the user -> Option D

4. Quick Check:

   Invoke calls Edge Functions [OK]

Hint: Invoke calls Edge Functions for fast user responses [OK]

Common Mistakes:

• Thinking it accesses database directly
• Confusing with file upload methods
• Assuming it creates users automatically

2. Which of the following is the correct syntax to invoke an Edge Function named hello using Supabase client in JavaScript?

easy

A. await supabase.functions.invoke('hello')

B. supabase.invoke.functions('hello')

C. await supabase.functions.call('hello')

D. supabase.functions.run('hello')

Solution

1. Step 1: Recall the correct method name

   The method to call Edge Functions is supabase.functions.invoke().

2. Step 2: Check the syntax for calling a function named 'hello'

   The correct syntax is await supabase.functions.invoke('hello').

3. Final Answer:

   await supabase.functions.invoke('hello') -> Option A

4. Quick Check:

   Correct method is invoke() [OK]

Hint: Use supabase.functions.invoke('functionName') [OK]

Common Mistakes:

• Using wrong method names like call or run
• Swapping order of functions and invoke
• Forgetting to await the async call

3. What will be the output of the following code snippet if the Edge Function returns {"message": "Hello World"}?

const { data, error } = await supabase.functions.invoke('greet');
if (error) {
  console.log('Error:', error.message);
} else {
  console.log(data.message);
}

medium

A. Hello World

B. Error: Function not found

C. undefined

D. SyntaxError

Solution

1. Step 1: Understand the function response

   The Edge Function returns an object with a key "message" and value "Hello World".

2. Step 2: Analyze the code output

   The code logs data.message which is "Hello World" if no error occurs.

3. Final Answer:

   Hello World -> Option A

4. Quick Check:

   data.message logs "Hello World" [OK]

Hint: Check data.message for function response output [OK]

Common Mistakes:

• Assuming error always occurs
• Confusing data with error object
• Expecting raw JSON string instead of parsed object

4. Identify the error in this code snippet that tries to invoke an Edge Function named dataFetch:

const response = supabase.functions.invoke('dataFetch')
console.log(response.data)

medium

A. No error, code is correct

B. Missing await keyword for the async invoke call

C. Using console.log instead of alert

D. Incorrect function name 'dataFetch'

Solution

1. Step 1: Check async call usage

   supabase.functions.invoke() returns a promise and must be awaited.

2. Step 2: Identify missing await

   The code assigns the promise to response without awaiting, so response.data is undefined.

3. Final Answer:

   Missing await keyword for the async invoke call -> Option B

4. Quick Check:

   Async calls need await [OK]

Hint: Always await async invoke calls [OK]

Common Mistakes:

• Forgetting await on async functions
• Assuming invoke returns data synchronously
• Ignoring promise nature of invoke()

5. You want to send JSON data {"userId": 123} to an Edge Function named getUserData and handle errors properly. Which code snippet correctly does this?

hard

A. const { data, error } = await supabase.functions.invoke('getUserData', body: { userId: 123 }); if (error) console.error(error); else console.log(data);

B. const { data, error } = supabase.functions.invoke('getUserData', { body: JSON.stringify({ userId: 123 }) }); if (error) console.error(error); else console.log(data);

C. const { data, error } = await supabase.functions.invoke('getUserData', { body: JSON.stringify({ userId: 123 }) }); if (error) console.error(error); else console.log(data);

D. const response = await supabase.functions.invoke('getUserData', { userId: 123 }); console.log(response.data);

Solution

1. Step 1: Understand the body format

   The body must be a JSON string, so use JSON.stringify() on the data object.

2. Step 2: Use await and handle error properly

   The call must be awaited and error checked before using data.

3. Final Answer:

   const { data, error } = await supabase.functions.invoke('getUserData', { body: JSON.stringify({ userId: 123 }) }); if (error) console.error(error); else console.log(data); -> Option C

4. Quick Check:

   Body as JSON string and await invoke [OK]

Hint: Stringify body JSON and await invoke call [OK]

Common Mistakes:

• Passing body as object instead of JSON string
• Not awaiting the invoke call
• Ignoring error handling