Error Propagation

Propagate errors through call stack

IntermediateTopic: Error Handling

JavaScript Error Propagation Program

This program helps you to learn the fundamental structure and syntax of JavaScript programming.

// Method 1: Re-throw error
function level1() {
    try {
        level2();
    } catch (error) {
        console.error('Level 1 caught:', error.message);
        throw error; // Re-throw
    }
}

function level2() {
    try {
        level3();
    } catch (error) {
        console.error('Level 2 caught:', error.message);
        throw error; // Re-throw
    }
}

function level3() {
    throw new Error('Error from level 3');
}

try {
    level1();
} catch (error) {
    console.error('Final catch:', error.message);
}

// Method 2: Wrap error
function processData(data) {
    try {
        return JSON.parse(data);
    } catch (error) {
        throw new Error(`Failed to process data: ${error.message}`);
    }
}

try {
    processData('invalid');
} catch (error) {
    console.error('Wrapped error:', error.message);
}

// Method 3: Error chain
class ChainedError extends Error {
    constructor(message, cause) {
        super(message);
        this.cause = cause;
        this.name = 'ChainedError';
    }
}

function operation1() {
    try {
        operation2();
    } catch (error) {
        throw new ChainedError('Operation 1 failed', error);
    }
}

function operation2() {
    throw new Error('Operation 2 failed');
}

try {
    operation1();
} catch (error) {
    console.error('Chained error:', error.message);
    console.error('Caused by:', error.cause.message);
}

// Method 4: Error handling middleware
function errorHandler(error, context) {
    console.error('Error in', context, ':', error.message);
    // Log to service, send notification, etc.
}

function riskyOperation() {
    try {
        throw new Error('Operation failed');
    } catch (error) {
        errorHandler(error, 'riskyOperation');
        throw error;
    }
}

Output

Level 3 caught: Error from level 3
Level 2 caught: Error from level 3
Level 1 caught: Error from level 3
Final catch: Error from level 3
Wrapped error: Failed to process data: Unexpected token i in JSON at position 0
Chained error: Operation 1 failed
Caused by: Operation 2 failed
Error in riskyOperation : Operation failed

Understanding Error Propagation

Error propagation moves errors up call stack.

Re-throwing

•Catch and re-throw

•Preserve original error

•Add context if needed

Wrapping Errors

•Wrap in new error

•Add context

•Preserve original

Error Chains

•Link errors

•Track cause

•Full error history

Error Middleware

•Centralized handling

•Logging

•Notifications

Best Practices

•Re-throw when appropriate

•Add context

•Don't swallow errors

•Log properly

Let us now understand every line and the components of the above program.

Note: To write and run JavaScript programs, you need to set up the local environment on your computer. Refer to the complete article Setting up JavaScript Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your JavaScript programs.

Async Error Handling

Custom Errors