# 【科学家养成日记#1】读取钱包代币数量

By [Ericet](https://paragraph.com/@ericet) · 2021-12-23

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最近看到一个笑话说，小的时候，我的愿望是成为一名科学家。长大后进入币圈，我的愿望还是成为一名科学家。可见科学家是个热门职业。

之前虽然有接触了一点合约，但是没有任何的实战经验。最近有个科学家群友在授课，所以报名参加学习一下科学家实战技术

第一堂课的第一个作业是，读取钱包里10个代币的数量

部分代码来自群友的教学，但是为了便于理解，进行了部分修改

    //加载web3的库
    const Web3 = require('web3');
    //读取ERC20的ABI文件
    const erc20Abi = require('./ABI/erc20.json');
    //设置BSC的RPC链接
    const rpcUrl = 'https://bsc-dataseed1.binance.org/';
    const rpcWeb3 = new Web3(new Web3.providers.HttpProvider(rpcUrl));
    
    let web3 = rpcWeb3;
    
    /**
     * 通过小数点多少位，转换对应的数据
     * tokenDecimals: 代币的小数点数
     * 
    **/
    function getWeiName(tokenDecimals = 18) {
        tokenDecimals = Number(tokenDecimals);
        let weiName = 'ether';
        switch (tokenDecimals) {
            case 3:
                weiName = "Kwei";
                break;
            case 6:
                weiName = 'mwei';
                break;
            case 9:
                weiName = 'gwei';
                break;
            case 12:
                weiName = 'microether ';
                break;
            case 15:
                weiName = 'milliether';
                break;
            case 18:
                weiName = 'ether';
                break;
            default:
                weiName = 'ether';
                break;
    
        }
        return weiName;
    }
    
    /**
     * 获得钱包BNB数量
     * address: 钱包地址
    **/
    const getBnbBalance = async (address) => {
        let result = await web3.eth.getBalance(address);
        if (result) {
            //经过小数点转换之后的BNB数量
            let balance = web3.utils.fromWei(result, getWeiName());
            return balance;
        } else {
            console.error("Getting Bnb Balance error.");
        }
    }
    
    /**
     * 获得钱包代币数量
     * tokenAddress: 代币合约地址
     * address: 钱包地址
    **/
    const getTokenBalance = async (tokenAddress, address) => {
        ////创建代币的智能合约函数
        let tokenContract = new web3.eth.Contract(erc20Abi, tokenAddress);
        //调用代币的智能合约获取余额功能
        let result = await tokenContract.methods.balanceOf(address).call();
        //获得代币有多少位小数
        let decimals = await tokenContract.methods.decimals().call();
        let weiName = getWeiName(decimals);
        let tokenBalance = web3.utils.fromWei(result, weiName);
        //获得代币的符号
        let symbol = await tokenContract.methods.symbol().call();
        return `${tokenBalance} ${symbol}`;
    }
    
    /**
     * 读取钱包里的10个代币的数量
    **/
    async function main() {
        let myWallet = '0x11e78fC4B70014d7B8978287bA3c5103D80dDd06';
        let walletBalance = await getBnbBalance(myWallet);
        console.log(`地址: ${myWallet} 有 ${walletBalance} BNB`);
        let tokens = [];
        tokens.push('0x55d398326f99059ff775485246999027b3197955');
        tokens.push('0x3fda9383a84c05ec8f7630fe10adf1fac13241cc');
        tokens.push('0x42712df5009c20fee340b245b510c0395896cf6e');
        tokens.push('0x373233A38ae21cF0C4f9DE11570E7D5Aa6824A1E');
        tokens.push('0x04645027122c9f152011f128c7085449b27cb6d7');
        tokens.push('0x740b40760266d54362c222c0490a95cf970cd199');
        tokens.push('0x7c357cd85bb600f748ec1d82adef74464c13e7a7');
        tokens.push('0xf0d585a29a86c25819526ba494100951dc31aa0b');
        tokens.push('0x366945ba85881b77c186597b4639683efeeb65ca');
        tokens.push('0xfb9f5738c9d767fea5af6e4d826ce18d1a48589a');
        for (let token of tokens) {
            let balance = await getTokenBalance(token, myWallet);
            console.log(`地址: ${myWallet} 有 ${balance}`);
        }
    }
    
    //启动程序
    main();
    

运行结果:

![](https://storage.googleapis.com/papyrus_images/93d5472f81eebad6db02e249b48ae14294ebb08f3cdd738d6f5a5bde56392efb.png)

源代码:

[https://github.com/ericet/kexuejia/blob/master/Lesson1Task1.js](https://github.com/ericet/kexuejia/blob/master/Lesson1Task1.js)

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*Originally published on [Ericet](https://paragraph.com/@ericet/1)*