Error Logging in JavaScript

1// Method 1: Simple error logger
2class ErrorLogger {
3    log(error, level = 'error') {
4        const logEntry = {
5            level: level,
6            message: error.message,
7            stack: error.stack,
8            timestamp: new Date().toISOString()
9        };
10        
11        console[level](JSON.stringify(logEntry, null, 2));
12    }
13}
14
15const logger = new ErrorLogger();
16try {
17    throw new Error('Test error');
18} catch (error) {
19    logger.log(error);
20}
21
22// Method 2: Structured logging
23class StructuredLogger {
24    log(error, metadata = {}) {
25        const logEntry = {
26            error: {
27                name: error.name,
28                message: error.message,
29                stack: error.stack
30            },
31            metadata: metadata,
32            timestamp: new Date().toISOString(),
33            environment: 'production'
34        };
35        
36        console.error(JSON.stringify(logEntry));
37    }
38}
39
40// Method 3: Error levels
41const LogLevel = {
42    DEBUG: 'debug',
43    INFO: 'info',
44    WARN: 'warn',
45    ERROR: 'error',
46    FATAL: 'fatal'
47};
48
49class LeveledLogger {
50    log(error, level = LogLevel.ERROR) {
51        const entry = {
52            level: level,
53            error: error.message,
54            timestamp: Date.now()
55        };
56        
57        if (level === LogLevel.ERROR || level === LogLevel.FATAL) {
58            entry.stack = error.stack;
59        }
60        
61        console.log(JSON.stringify(entry));
62    }
63}
64
65// Method 4: Error aggregation
66class ErrorAggregator {
67    constructor() {
68        this.errors = new Map();
69    }
70    
71    log(error) {
72        const key = error.message;
73        if (this.errors.has(key)) {
74            this.errors.get(key).count++;
75        } else {
76            this.errors.set(key, {
77                message: error.message,
78                count: 1,
79                firstSeen: Date.now(),
80                lastSeen: Date.now()
81            });
82        }
83    }
84    
85    getSummary() {
86        return Array.from(this.errors.values());
87    }
88}
89
90const aggregator = new ErrorAggregator();
91aggregator.log(new Error('Network error'));
92aggregator.log(new Error('Network error'));
93console.log('Summary:', aggregator.getSummary());