web3.js官方文档：https://web3js.readthedocs.io/
eth官方api：https://etherscan.io/apis
web3js奇客网：https://www.qikegu.com/docs/5127
rcpUrl获取：https://infura.io/dashboard

一、介绍

开发以太坊区块链应用程序，涉及到以下部分:

  • 智能合约开发 – 使用solidity语言编写代码，部署到区块链。
  • 网站或客户端开发 – 与区块链中的智能合约进行交互，读写数据。

在进行网站或客户端开发时，就需要用到web3.js。web3.js库是一个javascript库，可以让你执行很多与区块链进行交互的任务，例如：

  • 以太币转账
  • 读写智能合约中的数据
  • 创建智能合约

与Ajax类似，可以使用Web3.js读写以太坊区块链。

区块链网络是一个点对点的对等网络，网络由各个节点相互连接构成，智能合约的代码与数据存储在区块链中。

使用web3.js可以向区块链网络中某个以太坊节点发出请求，与区块链网络进行交互。

此过程如下图所示：
web3.js - 图1
web3.js使用JSON RPC与Ethereum区块链通信(JSON RPC即JSON远程调用)，对区块链网络进行数据读写。这有点像使用jQuery ajax库来读写web服务器上的数据。

二、环境搭建

安装 引入

  1. npm install web3
  3. import Web3 from 'web3'

连接以太坊节点

要访问以太坊网络，需要连接到Ethereum节点。
有几种方法可以做到这一点，可以使用Geth或Parity运行自己的Ethereum节点。但这需要从区块链下载大量数据并保持同步，很麻烦。
比较方便的方法是，使用Infura访问Ethereum节点。Infura是一个免费提供Ethereum节点的服务。
在Infura上注册账号，创建项目，在项目详情页上可以查看API KEY：
web3.js - 图2
使用API KEY，就可以访问以太坊网络节点。

三、访问区块链网络，读取余额

1、使用Infura URL，创建Web3连接。声明Infura URL变量：
2、确保使用之前获得的实际Infura API密钥替换此处的YOUR_INFURA_API_KEY。创建Web3连接:
3、读取余额 

  1. const rpcURL = "https://kovan.infura.io/v3/YOUR_INFURA_API_KEY"
  2. const web3 = new Web3(rpcURL)
  3. const address = "0x03118E2c88676d31ee397E1eEf7789fECfbC40b9"
  4. // 读取address中的余额，余额单位是wei
  5. web3.eth.getBalance(address, (err, wei) => {
  6.     // 余额单位从wei转换为ether
  7.     balance = web3.utils.fromWei(wei, 'ether')
  8.     console.log("balance: " + balance)
  9. })

4、获取测试eth
https://gitter.im/kovan-testnet/faucet
https://ethdrop.dev/

四、智能合约对象

1、介绍

智能合约对象是javascript中对智能合约的表示，可以使用智能合约对象访问智能合约。

对象可以使用web3.eth.Contract()函数获得，此函数需要2个参数: 智能合约ABI、智能合约地址。

ABI代表“Abstract Binary Interface/抽象二进制接口”，它是一个JSON数组，是面向以太坊虚拟机的可执行文件，类似于windows 平台上的二进制可执行文件。

智能合约编译后生成ABI文件，可以在以太坊虚拟机上执行。

2、获取ABI

获取ABI方法：（可以不填写ApiKey）

  1. const fetch = require('node-fetch');
  3. fetch('https://api.etherscan.io/api?module=contract&action=getabi&address={填入合约地址}&apikey={填入你的ApiKey}', {
  4.     method: 'get',
  5. }).then(response => response.json()
  6.   .then(data => console.log(data)));

这里有一个ABI的例子，这个例子是OmiseGo通证的ABI，它实现了ERC-20通证标准。

  1. const abi = [{"constant":true,"inputs":[],"name":"mintingFinished","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"name":"approve","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transferFrom","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"unpause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"}],"name":"mint","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"paused","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"}],"name":"balanceOf","outputs":[{"name":"balance","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"finishMinting","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"pause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transfer","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"},{"name":"_releaseTime","type":"uint256"}],"name":"mintTimelocked","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"remaining","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"payable":false,"type":"function"},{"anonymous":false,"inputs":[{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Mint","type":"event"},{"anonymous":false,"inputs":[],"name":"MintFinished","type":"event"},{"anonymous":false,"inputs":[],"name":"Pause","type":"event"},{"anonymous":false,"inputs":[],"name":"Unpause","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"owner","type":"address"},{"indexed":true,"name":"spender","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Transfer","type":"event"}]

你可以在Etherscan上，找到关于这个通证的更多细节，包括它的ABI及地址。我们将在这个示例的其余部分中使用这个智能合约ABI。

3、获取智能合约地址

可以在非小号、币安等平台查询代币的智能合约地址

OmiseGo通证智能合约的地址：

  1. const address = "0xd26114cd6EE289AccF82350c8d8487fedB8A0C07"

4、创建智能合约对象

有了ABI和地址，就可以创建OmiseGo通证智能合约的Javascript对象：

  1. const contract = new web3.eth.Contract(abi, address)

5、调用智能合约读函数

智能合约对象的methods属性下，包含了对应智能合约的所有函数。要调用智能合约中的某个函数，例如myFunction()，可以使用contract.methods.myFunction()的方式调用。

由于OmiseGo通证智能合约实现了ERC-20标准，应该已经实现了这些函数：totalSupply()、name()、symbol()和balanceOf()

  1. const Web3 = require('web3')
  2. const rpcURL = '' // Your RCP URL goes here
  3. const web3 = new Web3(rpcURL)
  5. const abi = [{"constant":true,"inputs":[],"name":"mintingFinished","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"name":"approve","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transferFrom","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"unpause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"}],"name":"mint","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"paused","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"}],"name":"balanceOf","outputs":[{"name":"balance","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"finishMinting","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"pause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transfer","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"},{"name":"_releaseTime","type":"uint256"}],"name":"mintTimelocked","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"remaining","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"payable":false,"type":"function"},{"anonymous":false,"inputs":[{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Mint","type":"event"},{"anonymous":false,"inputs":[],"name":"MintFinished","type":"event"},{"anonymous":false,"inputs":[],"name":"Pause","type":"event"},{"anonymous":false,"inputs":[],"name":"Unpause","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"owner","type":"address"},{"indexed":true,"name":"spender","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Transfer","type":"event"}]
  6. const address = '0xd26114cd6EE289AccF82350c8d8487fedB8A0C07'
  8. const contract = new web3.eth.Contract(abi, address)
  10. //查看现有OmiseGo通证的总供应量: 140245398245132780789239631
  11. contract.methods.totalSupply().call((err, result) => { console.log(result) })
  12. //查看OmiseGo通证的名称: OMGToken
  13. contract.methods.name().call((err, result) => { console.log(result) })
  14. //查看OmiseGo通证的标志: OMG
  15. contract.methods.symbol().call((err, result) => { console.log(result) })
  16. //查看给定账户的余额: 22620364140612904305860
  17. contract.methods.balanceOf('0xd26114cd6EE289AccF82350c8d8487fedB8A0C07').call((err, result) => { console.log(result) })
  • tips:这里调用方法只能调用读操作函数，不能调用写操作函数，写操作函数会改变区块链状态，调用写函数被视为交易。

五、交易操作

区块链中，交易操作是指会把数据写入区块链，改变区块链状态的操作。例如，以太币转账、调用写数据的智能合约函数，以及部署智能合约，这些操作都会改变区块链状态，被看作是交易。

1、安装ethereumjs-tx

根据区块链工作原理，创建交易时，会签署交易然后向网络广播。为了签署交易，我们使用JavaScript库ethereumjs-tx。
安装ethereumjs-tx

  1. npm install ethereumjs-tx

使用这个库的目的是，可以在本地签署交易。
要在本地签署交易，可以在本地运行自己的以太坊节点，这样就不必使用ethereumjs-tx库了。但是，如前所述，本地运行节点比较麻烦，需要同步区块链数据，相当繁琐，所以我们使用了Infura托管的远程节点。
如果在远程节点签署交易，就需要让远程节点管理我们的私钥，这是有风险的。所以最终我们选择了ethereumjs-tx来签署本地交易。

2、准备账号

接下来，我们将创建交易，签署交易，然后广播交易。
（1）引入ethereumjs-tx

  1. var Transaction = require('ethereumjs-tx').Transaction

（2）创建web3链接

  1. const web3 = new Web3('https://ropsten.infura.io/YOUR_INFURA_API_KEY')

（3）创建新账号

  1. web3.eth.accounts.create()

（4）把私钥设置为环境变量
把私钥设为环境变量，然后从代码中读取环境变量。这样就可以避免把私钥硬编码到源文件中，私钥是禁止公开的。
在Windows下设置环境变量：

  1. > SET PRIVATE_KEY_1='b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d'
  2. > SET PRIVATE_KEY_2='ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196'

在linux/mac下设置环境变量：

  1. sudo vi ~/.bash_profile
  3. $ export PRIVATE_KEY_1='b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d'
  4. $ export PRIVATE_KEY_2='ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196'

（5）声明账号和key
为了使用私钥对交易进行签名，必须使用缓冲区将它们转换成二进制数据字符串，缓冲区是NodeJS中的全局模块。

  1. const account1 = "0xc519cAB4dB0B3DdF6E55d44b97A99D5Ff491F494";
  2. const account2 = "0xff96B8B43ECd6C49805747F94747bFfa3A960b69";
  3. const privateKey1 = Buffer.from(process.env.PRIVATE_KEY_1)
  4. const privateKey2 = Buffer.from(process.env.PRIVATE_KEY_2)

3、执行交易

准备好了账号，就可以执行转账交易了。
交易可分为3个步骤：

  • 构建交易对象
  • 签署交易
  • 广播交易

（1）构建交易对象

  1. const txObject = {
  2.   nonce:    web3.utils.toHex(txCount),
  3.   to:       account2,
  4.   value:    web3.utils.toHex(web3.utils.toWei('0.1', 'ether')),
  5.   gasLimit: web3.utils.toHex(21000),
  6.   gasPrice: web3.utils.toHex(web3.utils.toWei('10', 'gwei'))
  7. }
  8. 参数解释：
  10. nonce – 这是账号的前一个交易计数。这个值必须是十六进制，可以使用Web3.js的web3.utils.toHex()转换。
  11. to – 目标账户。
  12. value – 要发送的以太币金额。这个值必须以十六进制表示，单位必须是wei。我们可以使用Web3.js工具web3.utils.toWei()转换单位。
  13. gasLimit – 交易能消耗Gas的上限。像这样的基本交易总是要花费21000单位的Gas。
  14. gasPrice – Gas价格，这里是 10 Gwei。

注意，这个交易对象中没有from字段。当使用account1的私钥签署这个交易时，它将被推算出来。
现在为nonce变量赋值，可以使用web3.eth.getTransactionCount()函数获取交易nonce。将构建交易对象的代码封装在一个回调函数中，如下所示:

  1. web3.eth.getTransactionCount(account1, (err, txCount) => {
  2.   const txObject = {
  3.     nonce:    web3.utils.toHex(txCount),
  4.     to:       account2,
  5.     value:    web3.utils.toHex(web3.utils.toWei('0.1', 'ether')),
  6.     gasLimit: web3.utils.toHex(21000),
  7.     gasPrice: web3.utils.toHex(web3.utils.toWei('10', 'gwei'))
  8.   }
  9. })

（2）签署交易

  1. const tx = new Tx(txObject)
  2. tx.sign(privateKey1)
  4. const serializedTx = tx.serialize()
  5. const raw = '0x' + serializedTx.toString('hex')

这里使用etheremjs-tx库来创建一个新的Tx对象，然后使用这个库与privateKey1签署交易。接着，序列化交易并转换为十六进制字符串，以便将其传递给Web3。
（3）广播交易
最后广播交易，可以使用web3.eth.sendSignedTransaction()函数将这个已签名的序列化交易发送到测试网络，如下所示:

  1. web3.eth.sendSignedTransaction(raw, (err, txHash) => {
  2.   console.log('txHash:', txHash)
  3. })

完成交易

4、总结

  1. var Tx     = require('ethereumjs-tx').Transaction
  2. const Web3 = require('web3')
  3. const web3 = new Web3('https://ropsten.infura.io/v3/YOUR_INFURA_API_KEY')
  5. const account1 = '0xf4Ab5314ee8d7AA0eB00b366c52cEEccC62d6B4B' // Your account address 1
  6. const account2 = '0xff96B8B43ECd6C49805747F94747bFfa3A960b69' // Your account address 2
  8. const pk1 = 'b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d' // 实际项目中应该从process.env.PRIVATE_KEY_1中读取
  9. const pk2 = 'ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196' // 实际项目中应该从process.env.PRIVATE_KEY_2中读取
  11. const privateKey1 = Buffer.from(pk1, 'hex')
  12. const privateKey2 = Buffer.from(pk2, 'hex')
  14. web3.eth.getTransactionCount(account1, (err, txCount) => {
  15.   // 创建交易对象
  16.   const txObject = {
  17.     nonce:    web3.utils.toHex(txCount),
  18.     to:       account2,
  19.     value:    web3.utils.toHex(web3.utils.toWei('0.1', 'ether')),
  20.     gasLimit: web3.utils.toHex(21000),
  21.     gasPrice: web3.utils.toHex(web3.utils.toWei('10', 'gwei'))
  22.   }
  24.   // 签署交易
  25.   const tx = new Tx(txObject, { chain: 'ropsten', hardfork: 'petersburg' })
  26.   tx.sign(privateKey1)
  28.   const serializedTx = tx.serialize()
  29.   const raw = '0x' + serializedTx.toString('hex')
  31.   // 广播交易
  32.   web3.eth.sendSignedTransaction(raw, (err, txHash) => {
  33.     console.log('txHash:', txHash)
  34.     // 可以去ropsten.etherscan.io查看交易详情
  35.   })
  36. })

运行后输出

  1. txHash: 0x4167cc0e35a750032be89f3c319026a5e7b2f0f93ac5c659a660e85a88053edf

可以去etherscan，查看交易详情

六、部署智能合约

七、调用智能合约写函数

八、智能合约事件

九、区块查询

十、常用工具

十一、连接bsc测试链

网络名称: BSC TEST
RPC URL:
https://data-seed-prebsc-1-s1.binance.org:8545/
https://data-seed-prebsc-2-s1.binance.org:8545/
https://data-seed-prebsc-1-s2.binance.org:8545/
https://data-seed-prebsc-2-s2.binance.org:8545/
https://data-seed-prebsc-1-s3.binance.org:8545/
https://data-seed-prebsc-2-s3.binance.org:8545/
链 ID: 97
符号: BNB
测试网浏览器 URL: https://testnet.bscscan.com/
测试网水龙头 URL: https://testnet.binance.org/faucet-smart
[

](https://blog.csdn.net/weixin_40042498/article/details/118399810)
向测试链钱包注入测试 BNB/USDT/DOGE

  • USDT: 0x6cd2Bf22B3CeaDfF6B8C226487265d81164396C5
  • DOGE: 0xD4af6aBBF19E677660D7982551b337Db06519C7A

其他操作
https://zhuanlan.zhihu.com/p/441020817