js callback 使用

function greet(name, callback) {
    console.log('Hello, ' + name);
    callback();
}

greet('Alice', function() {
    console.log('Callback executed!');
});

function delayedGreet(name, delay, callback) {
    setTimeout(function() {
        console.log('Hello, ' + name);
        callback();
    }, delay);
}

delayedGreet('Bob', 2000, function() {
    console.log('Delayed callback executed!');
});

function fetchData(url) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('Data fetched');
        }, 1000);
    });
}

fetchData('https://example.com/data')
    .then(data => {
        console.log(data);
    })
    .catch(error => {
        console.error(error);
    });

// 使用 Promise 避免回调地狱
function step1() {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve('Step 1 done'), 1000);
    });
}

function step2() {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve('Step 2 done'), 1000);
    });
}

step1()
    .then(result1 => {
        console.log(result1);
        return step2();
    })
    .then(result2 => {
        console.log(result2);
    });

// 使用 async/await
async function runSteps() {
    const result1 = await step1();
    console.log(result1);
    const result2 = await step2();
    console.log(result2);
}

runSteps();