JavaScript Async Await Undefined Promise Error Prevention Code

Prevent JavaScript async await not working undefined promise error with these production-ready utility functions. These code snippets provide robust error handling and debugging capabilities for async/await operations.

Core Error Prevention Utilities #

1. Safe Async Wrapper Function #

This utility ensures async functions always return meaningful values instead of undefined:

2. Promise State Debugger #

Debug promise states to identify when undefined values occur:

// Promise debugging utility
class PromiseDebugger {
    static async debug(promise, label = 'Promise') {
        console.log(`${label} - Starting...`);
        console.log(`${label} - State:`, promise);
        
        try {
            const result = await promise;
            console.log(`${label} - Resolved with:`, result);
            
            if (result === undefined) {
                console.warn(`${label} - WARNING: Resolved with undefined!`);
            }
            
            return result;
        } catch (error) {
            console.error(`${label} - Rejected with:`, error);
            throw error;
        }
    }
    
    static wrapAsync(asyncFn, label) {
        return async function(...args) {
            const promise = asyncFn.apply(this, args);
            return PromiseDebugger.debug(promise, label);
        };
    }
}

// Usage example
const debuggedFetch = PromiseDebugger.wrapAsync(
    async (url) => {
        const response = await fetch(url);
        return response.json();
    },
    'API Fetch'
);

3. Async Result Validator #

Validate async function results to catch undefined values early:

Error Handling Utilities #

4. Async Operation Manager #

Manage multiple async operations with guaranteed error handling:

// Async operation manager
class AsyncOperationManager {
    constructor() {
        this.operations = new Map();
    }
    
    async execute(operationId, asyncFn, options = {}) {
        const {
            timeout = 5000,
            retries = 3,
            defaultValue = null,
            onError = console.error
        } = options;
        
        this.operations.set(operationId, { status: 'pending', startTime: Date.now() });
        
        for (let attempt = 1; attempt <= retries; attempt++) {
            try {
                const timeoutPromise = new Promise((_, reject) => {
                    setTimeout(() => reject(new Error('Operation timeout')), timeout);
                });
                
                const result = await Promise.race([asyncFn(), timeoutPromise]);
                
                if (result === undefined) {
                    throw new Error('Async operation returned undefined');
                }
                
                this.operations.set(operationId, { 
                    status: 'completed', 
                    result, 
                    attempts: attempt 
                });
                
                return result;
            } catch (error) {
                onError(`Attempt ${attempt} failed:`, error);
                
                if (attempt === retries) {
                    this.operations.set(operationId, { 
                        status: 'failed', 
                        error, 
                        attempts: attempt 
                    });
                    return defaultValue;
                }
                
                // Wait before retry
                await new Promise(resolve => setTimeout(resolve, 1000 * attempt));
            }
        }
    }
    
    getOperationStatus(operationId) {
        return this.operations.get(operationId) || { status: 'not_found' };
    }
}

// Usage
const manager = new AsyncOperationManager();

manager.execute('fetch-users', async () => {
    const response = await fetch('/api/users');
    return response.json();
}, {
    timeout: 3000,
    retries: 2,
    defaultValue: []
}).then(users => console.log('Users:', users));

5. Promise Chain Error Interceptor #

Intercept and handle errors in promise chains to prevent undefined results:

Debugging and Monitoring Utilities #

6. Async Performance Monitor #

Monitor async operations for performance and error patterns:

// Async performance monitor
class AsyncPerformanceMonitor {
    constructor() {
        this.metrics = {
            totalOperations: 0,
            successfulOperations: 0,
            failedOperations: 0,
            undefinedResults: 0,
            averageResponseTime: 0,
            operations: []
        };
    }
    
    monitor(asyncFn, operationName = 'Anonymous') {
        return async (...args) => {
            const startTime = performance.now();
            const operationId = `${operationName}-${Date.now()}`;
            
            try {
                const result = await asyncFn(...args);
                const endTime = performance.now();
                const duration = endTime - startTime;
                
                this.recordSuccess(operationId, duration, result);
                
                if (result === undefined) {
                    this.metrics.undefinedResults++;
                    console.warn(`Operation ${operationName} returned undefined`);
                }
                
                return result;
            } catch (error) {
                const endTime = performance.now();
                const duration = endTime - startTime;
                
                this.recordFailure(operationId, duration, error);
                throw error;
            }
        };
    }
    
    recordSuccess(operationId, duration, result) {
        this.metrics.totalOperations++;
        this.metrics.successfulOperations++;
        this.updateAverageResponseTime(duration);
        
        this.metrics.operations.push({
            id: operationId,
            status: 'success',
            duration,
            timestamp: new Date().toISOString(),
            resultType: typeof result
        });
    }
    
    recordFailure(operationId, duration, error) {
        this.metrics.totalOperations++;
        this.metrics.failedOperations++;
        this.updateAverageResponseTime(duration);
        
        this.metrics.operations.push({
            id: operationId,
            status: 'failed',
            duration,
            timestamp: new Date().toISOString(),
            error: error.message
        });
    }
    
    updateAverageResponseTime(duration) {
        const total = this.metrics.averageResponseTime * (this.metrics.totalOperations - 1) + duration;
        this.metrics.averageResponseTime = total / this.metrics.totalOperations;
    }
    
    getReport() {
        return {
            ...this.metrics,
            successRate: this.metrics.successfulOperations / this.metrics.totalOperations * 100,
            undefinedRate: this.metrics.undefinedResults / this.metrics.totalOperations * 100
        };
    }
}

// Usage
const monitor = new AsyncPerformanceMonitor();

const monitoredFetch = monitor.monitor(async (url) => {
    const response = await fetch(url);
    return response.json();
}, 'API-Fetch');

// Generate report after operations
setTimeout(() => {
    console.log('Performance Report:', monitor.getReport());
}, 5000);

Implementation Examples #

Complete Error Prevention Setup #

Combine all utilities for comprehensive error prevention:

// Complete async error prevention setup
class AsyncErrorPrevention {
    constructor() {
        this.monitor = new AsyncPerformanceMonitor();
        this.manager = new AsyncOperationManager();
        this.debugMode = false;
    }
    
    enableDebugMode() {
        this.debugMode = true;
        return this;
    }
    
    createSafeAsyncFunction(asyncFn, options = {}) {
        const {
            name = 'AsyncOperation',
            defaultValue = null,
            timeout = 5000,
            retries = 1
        } = options;
        
        let wrappedFn = asyncFn;
        
        // Add monitoring
        wrappedFn = this.monitor.monitor(wrappedFn, name);
        
        // Add debugging if enabled
        if (this.debugMode) {
            wrappedFn = PromiseDebugger.wrapAsync(wrappedFn, name);
        }
        
        // Return safe wrapper
        return async (...args) => {
            return this.manager.execute(`${name}-${Date.now()}`, () => {
                return wrappedFn(...args);
            }, {
                timeout,
                retries,
                defaultValue
            });
        };
    }
    
    getSystemReport() {
        return {
            performance: this.monitor.getReport(),
            operations: Array.from(this.manager.operations.entries())
        };
    }
}

// Usage example
const errorPrevention = new AsyncErrorPrevention().enableDebugMode();

const safeApiCall = errorPrevention.createSafeAsyncFunction(
    async (endpoint) => {
        const response = await fetch(endpoint);
        return response.json();
    },
    {
        name: 'SafeAPICall',
        defaultValue: { error: 'No data available' },
        timeout: 3000,
        retries: 2
    }
);

Usage Tips #

1. Always wrap external async operations with error prevention utilities
2. Use default values to prevent undefined returns in critical paths
3. Monitor async operations in production to identify patterns
4. Enable debugging during development to catch issues early
5. Implement retries for network operations that might fail

These utilities provide comprehensive protection against JavaScript async await not working undefined promise error scenarios while maintaining code readability and performance.

For more error handling patterns, see our Async Error Handling Guide and Promise Debugging Techniques.