Using for directive in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to loop through each block in the blockchain.

Blockchain / Solidity

for block in [1] {
    // process block
}

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Aledger

Bchain

Cblocks

Dblockchain

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not hold the blocks.

Forgetting to use the correct variable name.

The variable blockchain holds the list of blocks to loop through.

2fill in blank

medium

Complete the code to print the hash of each block in the blockchain.

Blockchain / Solidity

for block in blockchain {
    print([1]);
}

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Ablock.hash

Bblock.previousHash

Cblock.data

Dblock.index

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the previous block's hash instead of the current block's hash.

Printing block data instead of the hash.

The hash property of each block contains its unique hash value.

3fill in blank

hard

Fix the error in the for loop to correctly iterate over the blockchain array.

Blockchain / Solidity

for (let [1] = 0; [1] < blockchain.length; [1]++) {
    console.log(blockchain[[1]].hash);
}

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Ai

Bblock

Cindex

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not consistent throughout the loop.

Using a variable name that conflicts with block objects.

The variable i is the conventional index variable used in for loops.

4fill in blank

hard

Fill both blanks to create a dictionary of block hashes and their data for blocks with index greater than 0.

Blockchain / Solidity

const blockData = {
  [1]: blockchain[[2]].data
  for [2] in blockchain if blockchain[[2]].index > 0
};

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Ablockchain[blockIndex].hash

BblockIndex

Dblock

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name for the loop.

Not accessing blockchain elements by index.

Use blockIndex as the loop variable and access the hash and data by index.

5fill in blank

hard

Fill both blanks to filter blocks with data value greater than 100 and create a new list of their hashes.

Blockchain / Solidity

const filteredHashes = blockchain.filter(block => block.data [1] 100).map(block => block.[2]);

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A>

Bhash

C<

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong comparison operator.

Mapping to the wrong property.

Use > to filter blocks with data greater than 100 and map to their hash.