web3.js（三）查询智能合约币数量（erc20）

需要获取到智能合约地址+智能合约ABI

1.打开https://etherscan.io/ 搜索cmt，跳转到该页面，点击红色区域，跳转到智能合约地址

2.address是智能合约地址，点击Contract Source 获取ABI

3.code：调用cmt智能合约的方法balanceOf()

 

const Web3 = require("web3");
const BigNumber = require('bignumber.js');
const Ether = new BigNumber(10e+17);
let web3 = new Web3(new Web3.providers.HttpProvider('https://api.myetherapi.com/eth'));
let abi = [
    {
        "constant": true,
        "inputs": [],
        "name": "name",
        "outputs": [{"name": "", "type": "string"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "_spender", "type": "address"}, {"name": "_value", "type": "uint256"}],
        "name": "approve",
        "outputs": [{"name": "", "type": "bool"}],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "totalSupply",
        "outputs": [{"name": "", "type": "uint256"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "_from", "type": "address"}, {"name": "_to", "type": "address"}, {
            "name": "_value",
            "type": "uint256"
        }],
        "name": "transferFrom",
        "outputs": [{"name": "", "type": "bool"}],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "INITIAL_SUPPLY",
        "outputs": [{"name": "", "type": "uint256"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "decimals",
        "outputs": [{"name": "", "type": "uint256"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [],
        "name": "unpause",
        "outputs": [],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "paused",
        "outputs": [{"name": "", "type": "bool"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "_spender", "type": "address"}, {"name": "_subtractedValue", "type": "uint256"}],
        "name": "decreaseApproval",
        "outputs": [{"name": "success", "type": "bool"}],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [{"name": "_owner", "type": "address"}],
        "name": "balanceOf",
        "outputs": [{"name": "balance", "type": "uint256"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [],
        "name": "pause",
        "outputs": [],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "owner",
        "outputs": [{"name": "", "type": "address"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [],
        "name": "symbol",
        "outputs": [{"name": "", "type": "string"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "_to", "type": "address"}, {"name": "_value", "type": "uint256"}],
        "name": "transfer",
        "outputs": [{"name": "", "type": "bool"}],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "_spender", "type": "address"}, {"name": "_addedValue", "type": "uint256"}],
        "name": "increaseApproval",
        "outputs": [{"name": "success", "type": "bool"}],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {
        "constant": true,
        "inputs": [{"name": "_owner", "type": "address"}, {"name": "_spender", "type": "address"}],
        "name": "allowance",
        "outputs": [{"name": "", "type": "uint256"}],
        "payable": false,
        "stateMutability": "view",
        "type": "function"
    }, {
        "constant": false,
        "inputs": [{"name": "newOwner", "type": "address"}],
        "name": "transferOwnership",
        "outputs": [],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function"
    }, {"inputs": [], "payable": false, "stateMutability": "nonpayable", "type": "constructor"}, {
        "anonymous": false,
        "inputs": [],
        "name": "Pause",
        "type": "event"
    }, {"anonymous": false, "inputs": [], "name": "Unpause", "type": "event"}, {
        "anonymous": false,
        "inputs": [{"indexed": true, "name": "previousOwner", "type": "address"}, {
            "indexed": true,
            "name": "newOwner",
            "type": "address"
        }],
        "name": "OwnershipTransferred",
        "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"
    }]
let addr = '0xf85fEea2FdD81d51177F6b8F35F0e6734Ce45F5F'
let metacoin = new web3.eth.Contract(abi, addr);
metacoin.methods.balanceOf('0x3f5CE5FBFe3E9af3971dD833D26bA9b5C936f0bE').call().then(v => {
    let ret = new BigNumber(v);
    return parseFloat(ret.dividedBy(Ether)).toFixed(2);
}).then(sum => {
    console.log(sum);
})