【跟乐乐学web3开发】一.使用IDE工具webstorm来编写web3js

前言

web3可以用java语言来编写，通过java的web3j依赖来编写，但是web3j对于abi的应用等支持库不太完整，所以还是多少有点局限性。
因此在当今的web3领域中，使用基于javaScript的web3.js库来编写web3应用是主流。
市面上大多的教材中，对于web3.js的编写是基于vscode这一款ide工具，这里我则是使用了webStorm来编写。
在使用webstorm编写web3应用前，需要确保你的环境已经安装了nodeJs以及npm。
同时，读者需要具有一定的javaScript基础，这样才能较好的利用api文档进行学习。

我的nodejs版本:v9.4.0
npm版本:5.6.0

一.web3的Api了解

在具有js基础上，我们通过web3的api文档，能够最快的实现和contract进行交互以及block扫描等操作。
api文档建议参考这两个：
https://web3js.readthedocs.io/en/v1.7.3/web3-eth-contract.html
https://www.qikegu.com/docs/5132

二.abi是什么？（重要）

根据一些类似官方的说法，abi是如下解释：

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。

是不是不好理解？
那么通俗来说，abi会用json形式，定义了你和contract交互时，能够调用哪些函数或者查看哪些变量。
比如，bsc中的绝大部分contract，都有一个叫做’decimals()'的函数，如果我想调用它，我就需要先在abi中以json形式声明这个函数的存在，之后进行调用。

这就类似于你在java中反射了一个类，想要调用它的方法，就需要准确的输入它的方法名一样。

三.建立web3项目

自定义你的项目路径

创建成功

安装web3js依赖
输入命令：

npm install web3

执行后，如果没有error则说明安装成功

四.编写一个简单的web3脚本

接下来，我们来编写一个简单的脚本，根据contract地址来获取它的符号。
新建一个叫demo的目录


新建一个demo脚本

脚本内容如下：

const Web3 = require('web3'); // 加载web3库
const web3Bsc = new Web3("https://bsc-dataseed1.binance.org:443"); // 通过web3库，连接bsc链上节点，从而实例化bsc链上web3节点对象。

// 定义abi，abi能够以json形式，规定能够和该contract的哪些函数或者变量进行交互，比如调用它get/set函数。
const abi = [{"inputs":[],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"spender","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"previousOwner","type":"address"},{"indexed":true,"internalType":"address","name":"newOwner","type":"address"}],"name":"OwnershipTransferred","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Transfer","type":"event"},{"constant":true,"inputs":[],"name":"_decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"_name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"_symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"spender","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"burn","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"subtractedValue","type":"uint256"}],"name":"decreaseAllowance","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"getOwner","outputs":[{"internalType":"address","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"addedValue","type":"uint256"}],"name":"increaseAllowance","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"mint","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"renounceOwnership","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}];
// 获取token符号（名称）
async function getTokenSymbol(){
    const contractAddress = new web3Bsc.eth.Contract(abi,"0x1d2f0da169ceb9fc7b3144628db156f3f6c60dbe");
    const symbol = await contractAddress.methods.symbol().call();//执行该contract中的'symbol()'函数。
    console.log(symbol);
}
getTokenSymbol();

执行

token符号成功获取到，并被打印出来了