Illustrating the Blockchain via SteemJs - Blocks are Chained

Blockchain is a fancy word, and not many people understand it. If you want to explain this to your GF/partner, what would be the most simple way?

Right, blocks are chained in one way, as time goes on, in particular for STEEM blockchain, every 3 seconds, we append a new block to the end of the current chain. So the chain goes longer and longer each day.

We need a way to tell if the current block can be attached (we can’t just produce a random block and force appending it). For each block, we will have a unique block ID, and we will have a previous field that match the previous Block ID. The first block on steem blockchain has previous set to 0000000000000000000000000000000000000000.

Run this in SteemJS

const blockNum = 1;
steem.api.getBlock(blockNum, function(err, result) {
  console.log(err, result);
});

You will see the block_id and previous value of the first block.

{"previous":"0000000000000000000000000000000000000000","timestamp":"2016-03-24T16:05:00","witness":"initminer","transaction_merkle_root":"0000000000000000000000000000000000000000","extensions":[],"witness_signature":"204f8ad56a8f5cf722a02b035a61b500aa59b9519b2c33c77a80c0a714680a5a5a7a340d909d19996613c5e4ae92146b9add8a7a663eef37d837ef881477313043","transactions":[],"block_id":"0000000109833ce528d5bbfb3f6225b39ee10086","signing_key":"STM8GC13uCZbP44HzMLV6zPZGwVQ8Nt4Kji8PapsPiNq1BK153XTX","transaction_ids":[]}

And the second block gives:

{"previous":"0000000109833ce528d5bbfb3f6225b39ee10086","timestamp":"2016-03-24T16:05:36","witness":"initminer","transaction_merkle_root":"0000000000000000000000000000000000000000","extensions":[],"witness_signature":"1f3e85ab301a600f391f11e859240f090a9404f8ebf0bf98df58eb17f455156e2d16e1dcfc621acb3a7acbedc86b6d2560fdd87ce5709e80fa333a2bbb92966df3","transactions":[],"block_id":"00000002ed04e3c3def0238f693931ee7eebbdf1","signing_key":"STM8GC13uCZbP44HzMLV6zPZGwVQ8Nt4Kji8PapsPiNq1BK153XTX","transaction_ids":[]}

As you can see, the previous value is the same as the block_id for the Block 1. This goes on and on. Let’s print the first 10 blocks’ previous and block_id:

Run the Code in SteemJS

function getBlock(blockNum) {
    return new Promise((resolve, reject) => {
        steem.api.getBlock(blockNum, function(err, result) {
            if (err) reject(err);
            resolve({
                block: blockNum,
                previous: result.previous,
                block_id: result.block_id,
            });
        });    
    });
}

(async function() {
    for (let i = 1; i <= 10; ++ i) {
        log(await getBlock(i));    
    }
})();

And you will see the rule applies. In fact, this is the fundamental rule of the blockchain - the rule to chain the blocks.

{"block":1,"previous":"0000000000000000000000000000000000000000","block_id":"0000000109833ce528d5bbfb3f6225b39ee10086"}
{"block":2,"previous":"0000000109833ce528d5bbfb3f6225b39ee10086","block_id":"00000002ed04e3c3def0238f693931ee7eebbdf1"}
{"block":3,"previous":"00000002ed04e3c3def0238f693931ee7eebbdf1","block_id":"000000035b094a812646289c622dba0ba67d1ffe"}
{"block":4,"previous":"000000035b094a812646289c622dba0ba67d1ffe","block_id":"00000004f9de0cfeb08c9d7d9d1fe536d902dc4a"}
{"block":5,"previous":"00000004f9de0cfeb08c9d7d9d1fe536d902dc4a","block_id":"00000005014b5562a1133070d8bee536de615329"}
{"block":6,"previous":"00000005014b5562a1133070d8bee536de615329","block_id":"00000006e323e35687e160b8aec86f1e56d4c902"}
{"block":7,"previous":"00000006e323e35687e160b8aec86f1e56d4c902","block_id":"000000079ff02a2dea6c4d9a27f752233d4a66b4"}
{"block":8,"previous":"000000079ff02a2dea6c4d9a27f752233d4a66b4","block_id":"000000084f957cc170a27c8330293a3343f82c23"}
{"block":9,"previous":"000000084f957cc170a27c8330293a3343f82c23","block_id":"00000009f35198cfd8a866868538bed3482d61a4"}
{"block":10,"previous":"00000009f35198cfd8a866868538bed3482d61a4","block_id":"0000000aae44a2f4d57170dab16fb1619f9e1d0e"}

Steem Blockchain is a public database. Every 3 seconds, one witness helps to package operations (comment, vote, transfer etc) into a block, seal it with the signing key, and finally push to the chain for a small reward.

As the blockchain gets bigger and bigger, it takes enormous efforts to alter the chain, as you will need to modify every prior blocks.

Every little helps! I hope this helps!

Steem On!~