Error Recovery in JavaScript

1// Method 1: Fallback values
2function fetchWithFallback(url, fallback) {
3    return fetch(url)
4        .then(response => response.json())
5        .catch(error => {
6            console.warn('Fetch failed, using fallback:', error);
7            return fallback;
8        });
9}
10
11// Method 2: Retry with fallback
12async function operationWithFallback(primary, fallback, maxRetries = 3) {
13    for (let i = 0; i < maxRetries; i++) {
14        try {
15            return await primary();
16        } catch (error) {
17            if (i === maxRetries - 1) {
18                console.warn('Primary failed, using fallback');
19                return await fallback();
20            }
21            await new Promise(resolve => setTimeout(resolve, 1000));
22        }
23    }
24}
25
26// Method 3: Circuit breaker
27class CircuitBreaker {
28    constructor(threshold = 5, timeout = 60000) {
29        this.failures = 0;
30        this.threshold = threshold;
31        this.timeout = timeout;
32        this.state = 'CLOSED'; // CLOSED, OPEN, HALF_OPEN
33        this.nextAttempt = Date.now();
34    }
35    
36    async execute(fn) {
37        if (this.state === 'OPEN') {
38            if (Date.now() < this.nextAttempt) {
39                throw new Error('Circuit breaker is OPEN');
40            }
41            this.state = 'HALF_OPEN';
42        }
43        
44        try {
45            const result = await fn();
46            this.onSuccess();
47            return result;
48        } catch (error) {
49            this.onFailure();
50            throw error;
51        }
52    }
53    
54    onSuccess() {
55        this.failures = 0;
56        this.state = 'CLOSED';
57    }
58    
59    onFailure() {
60        this.failures++;
61        if (this.failures >= this.threshold) {
62            this.state = 'OPEN';
63            this.nextAttempt = Date.now() + this.timeout;
64        }
65    }
66}
67
68const breaker = new CircuitBreaker();
69breaker.execute(() => fetch('https://api.example.com/data'));
70
71// Method 4: Graceful degradation
72function featureWithFallback(feature, fallback) {
73    try {
74        return feature();
75    } catch (error) {
76        console.warn('Feature unavailable, using fallback');
77        return fallback();
78    }
79}
80
81// Method 5: Error recovery strategies
82class RecoveryStrategy {
83    static async retry(fn, maxRetries) {
84        // Retry logic
85    }
86    
87    static async fallback(fn, fallbackFn) {
88        try {
89            return await fn();
90        } catch (error) {
91            return await fallbackFn();
92        }
93    }
94    
95    static async timeout(fn, timeoutMs, fallback) {
96        return Promise.race([
97            fn(),
98            new Promise((_, reject) => 
99                setTimeout(() => reject(new Error('Timeout')), timeoutMs)
100            )
101        ]).catch(() => fallback());
102    }
103}