createErrorHandler - Kequapp Documentation

import { createErrorHandler } from 'kequapp';

key	description	default
contentType *	Content type
action *	Action

Error handlers are invoked when an action throws an exception. They turn errors into useful information that is sent to a renderer in place of the expected response.

The createErrorHandler function must specify a contentType ('application/json', 'text/html', etc.) and an action to manipulate the information into a response.

The first parameter of an error handler is the error ex that has been thrown, after that it is the same as any action. It can return a value to invoke a renderer, finalize the response, change headers, or anything that you need.

Example

createErrorHandler({
    contentType: 'text/*',
    action: (ex, { url }) => {
        return `${url.pathname} ${ex.statusCode}: ${ex.message}`;
    },
});

Errors thrown within an error handler or the renderer it invokes will cause a fatal exception and an empty body will be delivered to the client.

For a good example of how to write an error handler see this repo's /src/built-in directory.

Kequapp will turn any error into json by default, and return a json formatted response. However this behavior can be overriden by writing your own error handlers that support more specific content types.

# createErrorHandler

Example