智能合约示例：
pragma solidity ^0.5.2; contract Coin { uint public val; event Set(uint val); function set(uint _val) public { val = _val; emit Set(_val); } function get() public view returns (uint) { return val; } }
html页面（请先下载web3.min.js，并放置在与当前html页面同文件夹下）
<html>
<head>
<meta charset="UTF-8">
<title>web3.js使用</title>
<script src="web3.min.js"></script>
<style type="text/css">
span {
display: inline-block;
}
</style>
</head>
<body>
<h1>web3.js与智能合约交互</h1>
<div id="info">444</div>
<span>
<input type="text" id="myVal"></input>
<button onclick="setVal()">修改</button>
</span>
<script>
//1、利用以太坊provider创建web3
var web3 = new Web3(new Web3.providers.HttpProvider("http://127.0.0.1:7545"));
//2、智能合约的abi，abi是由编译器生成的
var abi = [
{
"constant": true,
"inputs": [],
"name": "val",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": false,
"inputs": [
{
"name": "_val",
"type": "uint256"
}
],
"name": "set",
"outputs": [],
"payable": false,
"stateMutability": "nonpayable",
"type": "function"
},
{
"constant": true,
"inputs": [],
"name": "get",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"anonymous": false,
"inputs": [
{
"indexed": false,
"name": "val",
"type": "uint256"
}
],
"name": "Set",
"type": "event"
}
];
//3、根据abi获取合约
var ZombieFactoryContract = web3.eth.contract(abi);
//合约地址，发布之后在以太坊上生成的合约地址
var contractAddress = "0x18b490cddf021886af0e5f3129468533c0026da2";
//4、根据合约地址获取合约实例
var ZombieFactory = ZombieFactoryContract.at(contractAddress);
//5、监听合约中定义的事件, 执行UI操作，合约实例能访问合约中公共的函数以及事件
var event = ZombieFactory.Set(function(error, result) {
if (error) {
return
}
//console.log("9999");
//console.log(result.args.val.c);
document.getElementById("info").innerHTML = ZombieFactory.get();
});
//
function setVal(){
/**
*调用合约中的函数
*方式1：不会更改状态变量的函数调用方法 ZombieFactory.get()
*方式2：会更改状态变量的函数调用方法，需要发送交易 ZombieFactory.set.sendTransaction(函数参数, {from: web3.eth.accounts[0]})
*/
ZombieFactory.set.sendTransaction(document.getElementById("myVal").value, {from: web3.eth.accounts[0]});
}
</script>
</body>
</html>
--------------------------------------------
solidity语法：
a.sol合约文件
pragma solidity ^0.5.2; contract A { uint public x; uint public amount; constructor(uint _x) public payable { x = _x; } function get() public view returns (uint) { return x; } }
test.sol合约文件
pragma solidity ^0.5.2; import "./er.sol"; contract Coin { uint public val; A a; event Set(uint val); function set(uint _val) public { val = _val; a = new A(_val); emit Set(_val); } function get() public view returns (uint) { return val + a.get(); } }
--------------------
solidity的payable使用
payable 方法是让 Solidity 和以太坊变得如此酷的一部分 —— 它们修饰的函数是一种可以接收以太的特殊函数。
在以太坊中， 钱 (以太), 数据 (事务负载)， 以及合约代码本身都存在于以太坊。你可以在调用函数的同时付钱给另外一个合约。
合约 OnlineStore.sol如下：
pragma solidity ^0.5.2; contract a { function get() public payable { // 检查以确定0.001以太发送出去来运行函数 require(msg.value == 0.001 ether); // 如果requiretongguo，执行函数向调用者发送数字内容 // transferSomething(msg.sender); } }
在这里，msg.value 是可以查看向合约发送了多少以太的方法，另外 ether 是一个內建单元。
这里发生的事是，一些人会从 web3.js 调用这个函数 (从DApp的前端)， 像这样 :
// 假设 `OnlineStore` 在以太坊上指向你的合约: OnlineStore.get.sendTransaction({from: web3.eth.accounts[0], value: web3.toWei(0.001, 'ether')})；//该函数返回一个256位的值，类似 0x3b57fabc53f0bc6d6dec107d3d0cea2e3409683cf105a2766bf867768c0d9cf1 这种
-----------------------------
合约本身也是一个账户，当我们调用合约里定义的payable函数时，就会向合约发送一定数量的以太，这些以太就保存在合约账户里，我们也可以从合约中将这些以太提取到指定账户，如下使用示例：
pragma solidity ^0.5.2; contract Coin { uint public val; event Set(uint val); address public owner; constructor() public{ owner = msg.sender; } function set(uint _val) public payable { val = _val; emit Set(_val); } function get() public view returns (uint) { return val; } function balanceOf() public view returns (uint) { return owner.balance; } function balanceOfContract() public view returns (uint) { return address(this).balance; } }
<html>
<head>
<meta charset="UTF-8">
<title>web3.js使用</title>
<script src="web3.min.js"></script>
<style type="text/css">
span {
display: inline-block;
}
</style>
</head>
<body>
<h1>web3.js与智能合约交互</h1>
<div id="info">444</div>
<div id="balance">444</div>
<span>
<input type="text" id="myVal"></input>
<button onclick="setVal()">update</button>
</span>
<script>
//1、利用以太坊provider创建web3
var web3 = new Web3(new Web3.providers.HttpProvider("http://127.0.0.1:7545"));
//2、智能合约的abi，abi是由编译器生成的
var abi = [
{
"constant": false,
"inputs": [
{
"name": "_val",
"type": "uint256"
}
],
"name": "set",
"outputs": [],
"payable": true,
"stateMutability": "payable",
"type": "function"
},
{
"inputs": [],
"payable": false,
"stateMutability": "nonpayable",
"type": "constructor"
},
{
"anonymous": false,
"inputs": [
{
"indexed": false,
"name": "val",
"type": "uint256"
}
],
"name": "Set",
"type": "event"
},
{
"constant": true,
"inputs": [],
"name": "balanceOf",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": true,
"inputs": [],
"name": "balanceOfContract",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": true,
"inputs": [],
"name": "get",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": true,
"inputs": [],
"name": "owner",
"outputs": [
{
"name": "",
"type": "address"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": true,
"inputs": [],
"name": "val",
"outputs": [
{
"name": "",
"type": "uint256"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
}
];
//3、根据abi获取合约
var ZombieFactoryContract = web3.eth.contract(abi);
//合约地址，发布之后在以太坊上生成的合约地址
var contractAddress = "0xd6358db490163053a8a8c852c6397502278d0d97";
//4、根据合约地址获取合约实例
var ZombieFactory = ZombieFactoryContract.at(contractAddress);
//5、监听合约中定义的事件, 执行UI操作，合约实例能访问合约中公共的函数以及事件
var event = ZombieFactory.Set(function(error, result) {
if (error) {
return
}
//console.log("9999");
//console.log(result.args.val.c);
document.getElementById("info").innerHTML = ZombieFactory.get();
});
//
function setVal(){
/**
*调用合约中的函数
*方式1：不会更改状态变量的函数调用方法 ZombieFactory.get()
*方式2：会更改状态变量的函数调用方法，需要发送交易 ZombieFactory.set.sendTransaction(函数参数, {from: web3.eth.accounts[0]})
*/
ZombieFactory.set.sendTransaction(document.getElementById("myVal").value, {from: web3.eth.accounts[0], value: web3.toWei(0.001, 'ether')});
console.log(web3.eth.getBalance("0xa6c07AE626F0BB30Fe77f3f924c37CCa59895BAc"));
}
</script>
</body>
</html>
参考文章 https://www.jianshu.com/p/d7f620d23c5b