Web3.js communicates with the Ethereum Blockchain by using the JSON-RPC method or a Remote Procedure Call protocol.
Web3.js is a JavaScript library that lets a web page or Node.js application read blockchain data, send transactions and interact with smart contracts by talking to an Ethereum node.
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Blockchain
- A digital ledger (database) that is shared and synchronised among the nodes of a peer-to-peer network.
- Records are grouped into blocks, and each block is linked to the previous one by a cryptographic hash, so the history cannot be quietly changed.
- Blockchains are best known for keeping a secure, decentralized record of cryptocurrency transactions – but their use is not limited to cryptocurrency.
- Any industry can use a blockchain to make its records immutable – the term for data that cannot be altered once written.
Because every participant keeps a copy and new blocks are added only through consensus, a blockchain removes the need to trust a single middle-man. This course takes you from the very basics of data structures to Ethereum, smart contracts, tokens, DeFi and scaling – with notes, 15 practice questions and a 5-question MCQ test in every chapter.
Key Characteristics of Blockchain
Decentralization
No single authority controls the network; control is spread across many independent nodes.
Immutability
Confirmed blocks practically cannot be altered because every block is hash-linked to the one before it.
Transparency
On public blockchains every transaction can be inspected and verified by anyone.
Cryptographic Security
Hash functions protect integrity; digital signatures prove who authorised each transaction.
Consensus
Nodes follow shared rules (PoW, PoS …) to agree on which transactions are valid and in what order.
Programmability
Smart contracts let the blockchain run code automatically – enabling tokens, dApps and DeFi.