Transaction confirmation handling in Blockchain / Solidity - Mini Project: Build & Apply

Transaction confirmation handling

📖 Scenario: You are building a simple blockchain wallet app. When you send a transaction, you want to check how many confirmations it has received on the blockchain to know if it is secure.

🎯 Goal: Create a program that stores a transaction with its current confirmation count, sets a confirmation threshold, checks if the transaction is confirmed enough, and then prints a message about the confirmation status.

📋 What You'll Learn

Create a dictionary called transaction with keys 'id' and 'confirmations' and exact values 'tx123' and 2

Create a variable called confirmation_threshold and set it to 3

Create a boolean variable called is_confirmed that is True if transaction['confirmations'] is greater than or equal to confirmation_threshold, otherwise False

Print Transaction tx123 confirmed if is_confirmed is True, otherwise print Transaction tx123 pending

💡 Why This Matters

🌍 Real World

Blockchain wallets and explorers show transaction confirmation status to users so they know when their transactions are secure.

💼 Career

Understanding how to handle transaction confirmations is important for blockchain developers building wallets, exchanges, or monitoring tools.

1

Create the transaction data

Create a dictionary called transaction with keys 'id' and 'confirmations' and values 'tx123' and 2 respectively.

Blockchain / Solidity

# Create the transaction dictionary with id 'tx123' and confirmations 2
# Your code here

Hint

Use curly braces to create a dictionary with the exact keys and values.

2

Set the confirmation threshold

Create a variable called confirmation_threshold and set it to 3.

Blockchain / Solidity

transaction = {'id': 'tx123', 'confirmations': 2}
# Create confirmation_threshold variable and set it to 3
# Your code here

Hint

Just assign the number 3 to the variable confirmation_threshold.

3

Check if transaction is confirmed

Create a boolean variable called is_confirmed that is True if transaction['confirmations'] is greater than or equal to confirmation_threshold, otherwise False.

Blockchain / Solidity

transaction = {'id': 'tx123', 'confirmations': 2}
confirmation_threshold = 3
# Create is_confirmed variable using a comparison
# Your code here

Hint

Use the >= operator to compare confirmations with the threshold.

4

Print confirmation status

Print Transaction tx123 confirmed if is_confirmed is True, otherwise print Transaction tx123 pending.

Blockchain / Solidity

transaction = {'id': 'tx123', 'confirmations': 2}
confirmation_threshold = 3
is_confirmed = transaction['confirmations'] >= confirmation_threshold
# Print confirmation status message
# Your code here

Hint

Use an if-else statement and f-strings to print the correct message.

Practice

1. What does transaction confirmation mean in blockchain?

easy

A. It means the transaction is deleted from the blockchain.

B. It means the transaction is reversed by the user.

C. It means the transaction is pending and not yet sent.

D. It means the transaction is safely recorded on the blockchain.

Solution

1. Step 1: Understand transaction confirmation meaning

   Transaction confirmation means the blockchain network has recorded the transaction securely.

2. Step 2: Compare options with definition

   Only It means the transaction is safely recorded on the blockchain. correctly states that confirmation means safe recording on the blockchain.

3. Final Answer:

   It means the transaction is safely recorded on the blockchain. -> Option D

4. Quick Check:

   Transaction confirmation = safe recording [OK]

Hint: Confirmation means transaction is securely recorded [OK]

Common Mistakes:

• Confusing confirmation with transaction pending state
• Thinking confirmation means deletion or reversal
• Assuming confirmation means user approval

2. Which of the following is the correct way to wait for a transaction confirmation in JavaScript using async/await?

easy

A. await transaction.confirm();

B. transaction.wait();

C. await transaction.wait();

D. transaction.confirm();

Solution

1. Step 1: Identify correct async syntax

   To wait for a promise in JavaScript, use await before the async function call.

2. Step 2: Match function name for confirmation

   The standard method to wait for transaction confirmation is wait(), not confirm().

3. Final Answer:

   await transaction.wait(); -> Option C

4. Quick Check:

   Use await with wait() to confirm transaction [OK]

Hint: Use await with wait() method to confirm transaction [OK]

Common Mistakes:

• Forgetting to use await causing unresolved promises
• Using wrong method name like confirm()
• Calling wait() without await leading to no pause

3. What will be the output of this JavaScript code snippet?

async function confirmTx(tx) {
  const receipt = await tx.wait();
  return receipt.confirmations;
}

const fakeTx = {
  wait: () => Promise.resolve({ confirmations: 3 })
};

confirmTx(fakeTx).then(console.log);

medium

A. 3

B. Promise {<pending>}

C. undefined

D. Error: wait is not a function

Solution

1. Step 1: Understand async function behavior

   The function confirmTx awaits tx.wait() which resolves to an object with confirmations: 3.

2. Step 2: Return and log confirmations

   The function returns receipt.confirmations which is 3, and then(console.log) prints 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Await wait() returns confirmations = 3 [OK]

Hint: Await returns resolved value, then log confirmations [OK]

Common Mistakes:

• Expecting Promise instead of resolved value
• Confusing property name confirmations
• Missing await causing Promise output

4. Identify the error in this code snippet for waiting transaction confirmation:

async function waitForConfirmation(tx) {
  const receipt = tx.wait();
  console.log(receipt.confirmations);
}

waitForConfirmation(transaction);

medium

A. Missing await before tx.wait()

B. Incorrect property name confirmations

C. Function should not be async

D. console.log should be outside the function

Solution

1. Step 1: Check async call usage

   The function calls tx.wait() which returns a Promise, but does not use await.

2. Step 2: Understand consequences of missing await

   Without await, receipt is a Promise object, so receipt.confirmations is undefined.

3. Final Answer:

   Missing await before tx.wait() -> Option A

4. Quick Check:

   Always await async calls to get resolved value [OK]

Hint: Always await async calls to get actual result [OK]

Common Mistakes:

• Not using await with async functions
• Assuming Promise has properties directly
• Misplacing console.log inside async function

5. You want to wait for at least 5 confirmations before proceeding with a transaction. Which code snippet correctly implements this logic?

hard

A. const receipt = await tx.wait(5); if(receipt.confirmations < 5) { proceed(); }

B. const receipt = await tx.wait(5); if(receipt.confirmations >= 5) { proceed(); }

C. const receipt = await tx.wait(3); if(receipt.confirmations >= 5) { proceed(); }

D. const receipt = await tx.wait(); if(receipt.confirmations == 5) { proceed(); }

Solution

1. Step 1: Use wait() with confirmation count

   Calling tx.wait(5) waits until at least 5 confirmations are reached.

2. Step 2: Check confirmations before proceeding

   Check if receipt.confirmations >= 5 to ensure safe confirmation before calling proceed().

3. Final Answer:

   const receipt = await tx.wait(5); if(receipt.confirmations >= 5) { proceed(); } -> Option B

4. Quick Check:

   wait(5) ensures 5 confirmations before proceed [OK]

Hint: Use wait(5) and check confirmations >= 5 before proceed [OK]

Common Mistakes:

• Waiting fewer confirmations than needed
• Checking for exact 5 instead of >= 5
• Proceeding when confirmations are less than required