js业务代码大全

document.querySelector('form').addEventListener('submit', function(event) {
    const input = document.querySelector('#myInput');
    if (input.value.trim() === '') {
        alert('输入不能为空');
        event.preventDefault(); // 阻止表单提交
    }
});

fetch('https://api.example.com/data')
    .then(response => response.json())
    .then(data => console.log(data))
    .catch(error => console.error('Error:', error));

const element = document.createElement('div');
element.textContent = 'Hello, World!';
document.body.appendChild(element);

document.querySelector('#myButton').addEventListener('click', function() {
    alert('按钮被点击了！');
});

// 延迟3秒后执行
setTimeout(() => {
    console.log('3秒后执行');
}, 3000);

// 每隔1秒执行一次
const intervalId = setInterval(() => {
    console.log('每隔1秒执行一次');
}, 1000);

// 清除定时器
setTimeout(() => {
    clearInterval(intervalId);
}, 5000);

const jsonData = '{"name": "Alice", "age": 25}';
const obj = JSON.parse(jsonData);
console.log(obj.name); // 输出: Alice

const newObj = { name: 'Bob', age: 30 };
const jsonString = JSON.stringify(newObj);
console.log(jsonString); // 输出: {"name":"Bob","age":30}

try {
    // 可能会抛出错误的代码
    throw new Error('Something went wrong');
} catch (error) {
    console.error('Error:', error.message);
} finally {
    console.log('无论是否发生错误，都会执行');
}

const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map(num => num * 2);
console.log(doubled); // 输出: [2, 4, 6, 8, 10]

const filtered = numbers.filter(num => num % 2 === 0);
console.log(filtered); // 输出: [2, 4]

// math.js
export function add(a, b) {
    return a + b;
}

// main.js
import { add } from './math.js';
console.log(add(2, 3)); // 输出: 5

import React from 'react';
import ReactDOM from 'react-dom';

function App() {
    return <h1>Hello, React!</h1>;
}

ReactDOM.render(<App />, document.getElementById('root'));