eth_blockNumber | Polygon

Polygon API method that returns the latest block number of the blockchain. A block number is a hexadecimal number representing the block’s position in the blockchain. For example, the block number 0x69B5B means that the block is the 432,987th block in the blockchain.

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Parameters

• none

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Response

• result — the integer value of the node’s latest block number is synced to encoded as hexadecimal. The block number is used to identify the block’s position in the blockchain and is updated every time a new block is added to the chain.

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eth_blockNumber code examples

const Web3 = require("web3");
const NODE_URL = "CHAINSTACK_NODE_URL";
const web3 = new Web3(NODE_URL);

async function getLatestBlockNumber() {
  const block = await web3.eth.getBlockNumber();
  console.log(`Latest block: ${block}`);
}
  
getLatestBlockNumber()

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Use case

A possible use case for the eth_blockNumber method in Ethereum is for applications that need to be aware of the current block number—some applications may need to be mindful of the current block number to function correctly. For example, a DApp may use the current block number to determine the expiration date of a time-limited offer.

The following code uses the web3.js library and defines a function called getCurrentBlockNumber. When called, this function returns the latest block number from the network, and you can use it in your DApp.

const Web3 = require('web3');

// Connect to the Ethereum network
const node_url = "CHAINSTACK_NODE_URL";
const web3 = new Web3(node_url);

// Define a function that returns the current block number
async function getCurrentBlockNumber() {
  const blockNumber = await web3.eth.getBlockNumber();
  return blockNumber;
};

// Use the getCurrentBlockNumber function in your application
async function main() {

  // Let's say you want to offer a special price on a service to a specific user.
  // Offer expires in a week, Polygon produces 1 block every 2 seconds which means 285600 block per week
  const blockInAWeek = 285600;
  const currentBlockNumber = await getCurrentBlockNumber();
  const offerExpires = currentBlockNumber + blockInAWeek;

  console.log(`Your special offer will expire on block: ${offerExpires}`);
};

main();

You can then use your application’s getCurrentBlockNumber function to get the current block number whenever you need it. In this example, we use it to calculate on which block a special offer to a specific user will expire. We retrieve the block when we issue the offer to the user and add 50400, which is approximately how many Ethereum blocks are produced weekly. Now, in the offerExpires constant, we have the last block when the user can exercise the special price.

Use the getCurrentBlockNumber function to compare it to offerExpires to know if the offer is still valid.