Async Error Handling in JavaScript

1// Method 1: Async/await with try-catch
2async function fetchData() {
3    try {
4        const response = await fetch('https://api.example.com/data');
5        if (!response.ok) {
6            throw new Error(`HTTP error! status: ${response.status}`);
7        }
8        const data = await response.json();
9        return data;
10    } catch (error) {
11        console.error('Fetch error:', error.message);
12        throw error;
13    }
14}
15
16fetchData().catch(error => {
17    console.error('Unhandled:', error);
18});
19
20// Method 2: Promise error handling
21function promiseOperation() {
22    return new Promise((resolve, reject) => {
23        setTimeout(() => {
24            if (Math.random() > 0.5) {
25                reject(new Error('Random failure'));
26            } else {
27                resolve('Success');
28            }
29        }, 1000);
30    });
31}
32
33promiseOperation()
34    .then(result => console.log('Result:', result))
35    .catch(error => console.error('Error:', error.message));
36
37// Method 3: Multiple async operations
38async function fetchMultiple() {
39    try {
40        const [data1, data2, data3] = await Promise.all([
41            fetch('https://api.example.com/data1').then(r => r.json()),
42            fetch('https://api.example.com/data2').then(r => r.json()),
43            fetch('https://api.example.com/data3').then(r => r.json())
44        ]);
45        return [data1, data2, data3];
46    } catch (error) {
47        console.error('One or more requests failed:', error);
48        throw error;
49    }
50}
51
52// Method 4: Promise.allSettled
53async function fetchAllSettled() {
54    const results = await Promise.allSettled([
55        fetch('https://api.example.com/data1'),
56        fetch('https://api.example.com/data2'),
57        fetch('https://api.example.com/data3')
58    ]);
59    
60    results.forEach((result, index) => {
61        if (result.status === 'fulfilled') {
62            console.log(`Request ${index + 1} succeeded`);
63        } else {
64            console.error(`Request ${index + 1} failed:`, result.reason);
65        }
66    });
67}
68
69// Method 5: Unhandled promise rejection
70process.on('unhandledRejection', (reason, promise) => {
71    console.error('Unhandled rejection:', reason);
72});
73
74// Method 6: Async error wrapper
75function asyncHandler(fn) {
76    return (req, res, next) => {
77        Promise.resolve(fn(req, res, next)).catch(next);
78    };
79}
80
81// Usage in Express
82const asyncRoute = asyncHandler(async (req, res) => {
83    const data = await fetchData();
84    res.json(data);
85});