Ethereum series - Web3 js

Web3.js

web3.js Is a set of interfaces used to interact with local or remote Ethereum nodes js library , It can be used HTTP or IPC Establish a connection with the Ethereum node .
On the bottom implementation , It passes through RPC Call to communicate with local or remote nodes .web3.js Can be exposed with any RPC Ethernet node connection of interface .

Installation

npm install web3

Usage

// In Node.js
const Web3 = require('web3');

let web3 = new Web3('ws://localhost:8546');
console.log(web3);
> {
    
    eth: ... ,
    shh: ... ,
    utils: ...,
    ...
}

0.20.X And 1.X Differences in versions

This is a web3.js There are two main types of versions

• use truffle migrate or truffle test It will be installed with the operating system web3js edition , It can be used truffle verson see
• nodejs Will use package.json Specified in the web3js Version number

1.x Version changes

• if ('utils' in web3) This judgment can be used web3j Version of
• web3.sha3 By web3.utils.sha3 replace
  • The data to be hashed is called web3.utils.sha3 You need to judge the empty space first : if (!input || !input.length) { return; }
• web3.eth.accounts is deprecated. Use web3.eth.getAccounts() instead
• web3.fromWei By web3.utils.fromWei replace
• web3.toWei By web3.utils.toWei replace
• watch No longer supported .
  • myContract.EventName([params]).watch([callback]) By myContract.EventName([params],[callback]) replace
• The HTTP provider is deprecated, as it won’t work for subscriptions. Have to use websocket
  • truffle-config.js in websockets: true
  • HttpProvider By WebsocketProvider replace , The port number does not need to be changed
  • network_local.json Medium rpcUrl configure ws://127.0.0.1:9545

Old projects want to compile

# package.json Middle configuration 
"web3": "^0.20.0",

# npm when 
npm install --force

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