Express Global Error Handler

javascript Copy Code

class AppError extends Error {
    constructor(message, statusCode, code = 'INTERNAL_ERROR') {
        super(message);
        this.statusCode = statusCode;
        this.code = code;
        this.isOperational = true;
        Error.captureStackTrace(this, this.constructor);
    }
}

const errorHandler = (err, req, res, next) => {
    err.statusCode = err.statusCode || 500;

    // Log error (only stack for 500s)
    if (err.statusCode >= 500) {
        console.error(`[${new Date().toISOString()}] ${err.stack}`);
    }

    // Mongoose validation error
    if (err.name === 'ValidationError') {
        const messages = Object.values(err.errors).map(e => e.message);
        return res.status(400).json({
            success: false,
            code: 'VALIDATION_ERROR',
            errors: messages
        });
    }

    // Mongoose duplicate key
    if (err.code === 11000) {
        const field = Object.keys(err.keyValue)[0];
        return res.status(409).json({
            success: false,
            code: 'DUPLICATE_KEY',
            message: `${field} already exists`
        });
    }

    res.status(err.statusCode).json({
        success: false,
        code: err.code || 'INTERNAL_ERROR',
        message: err.isOperational ? err.message : 'Something went wrong'
    });
};

module.exports = { AppError, errorHandler };

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